2017-11-27 15:37:16 +00:00
|
|
|
/*-
|
|
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
|
|
*
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
* Copyright (c) 2019 Google LLC
|
2001-07-09 10:35:18 +00:00
|
|
|
* Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank
|
|
|
|
* Copyright (c) 1995 Martin Husemann
|
|
|
|
*
|
|
|
|
* Redistribution and use in source and binary forms, with or without
|
|
|
|
* modification, are permitted provided that the following conditions
|
|
|
|
* are met:
|
|
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
|
|
* notice, this list of conditions and the following disclaimer.
|
|
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
|
|
* documentation and/or other materials provided with the distribution.
|
|
|
|
*
|
|
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
|
|
|
|
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
|
|
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
|
|
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
|
|
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
|
|
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
|
|
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
|
|
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
|
|
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
|
|
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
|
|
#include <sys/cdefs.h>
|
|
|
|
#ifndef lint
|
2012-10-21 12:01:11 +00:00
|
|
|
__RCSID("$NetBSD: fat.c,v 1.18 2006/06/05 16:51:18 christos Exp $");
|
2001-07-09 10:35:18 +00:00
|
|
|
static const char rcsid[] =
|
|
|
|
"$FreeBSD$";
|
|
|
|
#endif /* not lint */
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
#include <sys/endian.h>
|
|
|
|
#include <sys/queue.h>
|
|
|
|
#include <sys/limits.h>
|
|
|
|
#include <sys/mman.h>
|
|
|
|
#include <sys/param.h>
|
|
|
|
|
|
|
|
#include <assert.h>
|
|
|
|
#include <stdbool.h>
|
2001-07-09 10:35:18 +00:00
|
|
|
#include <stdlib.h>
|
|
|
|
#include <string.h>
|
|
|
|
#include <ctype.h>
|
|
|
|
#include <stdio.h>
|
|
|
|
#include <unistd.h>
|
|
|
|
|
|
|
|
#include "ext.h"
|
|
|
|
#include "fsutil.h"
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
static int _readfat(struct fat_descriptor *);
|
|
|
|
static inline struct bootblock* boot_of_(struct fat_descriptor *);
|
|
|
|
static inline int fd_of_(struct fat_descriptor *);
|
|
|
|
static inline bool valid_cl(struct fat_descriptor *, cl_t);
|
Reduce memory footprint of fsck_msdosfs.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-01 07:43:08 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Head bitmap for FAT scanning.
|
|
|
|
*
|
|
|
|
* FAT32 have up to 2^28 = 256M entries, and FAT16/12 have much less.
|
|
|
|
* For each cluster, we use 1 bit to represent if it's a head cluster
|
|
|
|
* (the first cluster of a cluster chain).
|
|
|
|
*
|
|
|
|
* Head bitmap
|
|
|
|
* ===========
|
|
|
|
* Initially, we set all bits to 1. In readfat(), we traverse the
|
|
|
|
* whole FAT and mark each cluster identified as "next" cluster as
|
|
|
|
* 0. After the scan, we have a bitmap with 1's to indicate the
|
|
|
|
* corresponding cluster was a "head" cluster.
|
|
|
|
*
|
|
|
|
* We use head bitmap to identify lost chains: a head cluster that was
|
|
|
|
* not being claimed by any file or directories is the head cluster of
|
|
|
|
* a lost chain.
|
|
|
|
*
|
|
|
|
* Handle of lost chains
|
|
|
|
* =====================
|
|
|
|
* At the end of scanning, we can easily find all lost chain's heads
|
|
|
|
* by finding out the 1's in the head bitmap.
|
|
|
|
*/
|
|
|
|
|
|
|
|
typedef struct long_bitmap {
|
|
|
|
unsigned long *map;
|
|
|
|
size_t count; /* Total set bits in the map */
|
|
|
|
} long_bitmap_t;
|
|
|
|
|
|
|
|
static inline void
|
|
|
|
bitmap_clear(long_bitmap_t *lbp, cl_t cl)
|
|
|
|
{
|
|
|
|
cl_t i = cl / LONG_BIT;
|
|
|
|
unsigned long clearmask = ~(1UL << (cl % LONG_BIT));
|
|
|
|
|
|
|
|
assert((lbp->map[i] & ~clearmask) != 0);
|
|
|
|
lbp->map[i] &= clearmask;
|
|
|
|
lbp->count--;
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline bool
|
|
|
|
bitmap_get(long_bitmap_t *lbp, cl_t cl)
|
|
|
|
{
|
|
|
|
cl_t i = cl / LONG_BIT;
|
|
|
|
unsigned long usedbit = 1UL << (cl % LONG_BIT);
|
|
|
|
|
|
|
|
return ((lbp->map[i] & usedbit) == usedbit);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline bool
|
|
|
|
bitmap_none_in_range(long_bitmap_t *lbp, cl_t cl)
|
|
|
|
{
|
|
|
|
cl_t i = cl / LONG_BIT;
|
|
|
|
|
|
|
|
return (lbp->map[i] == 0);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline size_t
|
|
|
|
bitmap_count(long_bitmap_t *lbp)
|
|
|
|
{
|
|
|
|
return (lbp->count);
|
|
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
|
|
bitmap_ctor(long_bitmap_t *lbp, size_t bits, bool allone)
|
|
|
|
{
|
|
|
|
size_t bitmap_size = roundup2(bits, LONG_BIT) / (LONG_BIT / 8);
|
|
|
|
|
|
|
|
free(lbp->map);
|
|
|
|
lbp->map = calloc(1, bitmap_size);
|
|
|
|
if (lbp->map == NULL)
|
|
|
|
return FSFATAL;
|
|
|
|
|
|
|
|
if (allone) {
|
|
|
|
memset(lbp->map, 0xff, bitmap_size);
|
|
|
|
lbp->count = bits;
|
|
|
|
} else {
|
|
|
|
lbp->count = 0;
|
|
|
|
}
|
|
|
|
return FSOK;
|
|
|
|
}
|
|
|
|
|
|
|
|
static void
|
|
|
|
bitmap_dtor(long_bitmap_t *lbp)
|
|
|
|
{
|
|
|
|
free(lbp->map);
|
|
|
|
lbp->map = NULL;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* FAT32 can be as big as 256MiB (2^26 entries * 4 bytes), when we
|
|
|
|
* can not ask the kernel to manage the access, use a simple LRU
|
|
|
|
* cache with chunk size of 128 KiB to manage it.
|
|
|
|
*/
|
|
|
|
struct fat32_cache_entry {
|
|
|
|
TAILQ_ENTRY(fat32_cache_entry) entries;
|
|
|
|
uint8_t *chunk; /* pointer to chunk */
|
|
|
|
off_t addr; /* offset */
|
|
|
|
bool dirty; /* dirty bit */
|
|
|
|
};
|
|
|
|
|
|
|
|
static const size_t fat32_cache_chunk_size = 131072; /* MAXPHYS */
|
|
|
|
static const size_t fat32_cache_size = 4194304;
|
|
|
|
static const size_t fat32_cache_entries = 32; /* XXXgcc: cache_size / cache_chunk_size */
|
|
|
|
|
|
|
|
/*
|
|
|
|
* FAT table descriptor, represents a FAT table that is already loaded
|
|
|
|
* into memory.
|
|
|
|
*/
|
|
|
|
struct fat_descriptor {
|
|
|
|
struct bootblock *boot;
|
|
|
|
uint8_t *fatbuf;
|
|
|
|
cl_t (*get)(struct fat_descriptor *, cl_t);
|
|
|
|
int (*set)(struct fat_descriptor *, cl_t, cl_t);
|
|
|
|
long_bitmap_t headbitmap;
|
|
|
|
int fd;
|
|
|
|
bool is_mmapped;
|
|
|
|
bool use_cache;
|
|
|
|
size_t fatsize;
|
|
|
|
|
|
|
|
size_t fat32_cached_chunks;
|
|
|
|
TAILQ_HEAD(cachehead, fat32_cache_entry) fat32_cache_head;
|
|
|
|
struct fat32_cache_entry *fat32_cache_allentries;
|
|
|
|
off_t fat32_offset;
|
|
|
|
off_t fat32_lastaddr;
|
|
|
|
};
|
|
|
|
|
|
|
|
void
|
|
|
|
fat_clear_cl_head(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
bitmap_clear(&fat->headbitmap, cl);
|
|
|
|
}
|
|
|
|
|
|
|
|
bool
|
|
|
|
fat_is_cl_head(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
return (bitmap_get(&fat->headbitmap, cl));
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline bool
|
|
|
|
fat_is_cl_head_in_range(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
return (!(bitmap_none_in_range(&fat->headbitmap, cl)));
|
|
|
|
}
|
|
|
|
|
|
|
|
static size_t
|
|
|
|
fat_get_head_count(struct fat_descriptor *fat)
|
|
|
|
{
|
|
|
|
return (bitmap_count(&fat->headbitmap));
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* FAT12 accessors.
|
|
|
|
*
|
|
|
|
* FAT12s are sufficiently small, expect it to always fit in the RAM.
|
|
|
|
*/
|
|
|
|
static inline uint8_t *
|
|
|
|
fat_get_fat12_ptr(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
return (fat->fatbuf + ((cl + (cl >> 1))));
|
|
|
|
}
|
|
|
|
|
|
|
|
static cl_t
|
|
|
|
fat_get_fat12_next(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
const uint8_t *p;
|
|
|
|
cl_t retval;
|
|
|
|
|
|
|
|
p = fat_get_fat12_ptr(fat, cl);
|
|
|
|
retval = le16dec(p);
|
|
|
|
/* Odd cluster: lower 4 bits belongs to the subsequent cluster */
|
|
|
|
if ((cl & 1) == 1)
|
|
|
|
retval >>= 4;
|
|
|
|
retval &= CLUST12_MASK;
|
|
|
|
|
|
|
|
if (retval >= (CLUST_BAD & CLUST12_MASK))
|
|
|
|
retval |= ~CLUST12_MASK;
|
|
|
|
|
|
|
|
return (retval);
|
|
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
|
|
fat_set_fat12_next(struct fat_descriptor *fat, cl_t cl, cl_t nextcl)
|
|
|
|
{
|
|
|
|
uint8_t *p;
|
|
|
|
|
|
|
|
/* Truncate 'nextcl' value, if needed */
|
|
|
|
nextcl &= CLUST12_MASK;
|
|
|
|
|
|
|
|
p = fat_get_fat12_ptr(fat, cl);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Read in the 4 bits from the subsequent (for even clusters)
|
|
|
|
* or the preceding (for odd clusters) cluster and combine
|
|
|
|
* it to the nextcl value for encoding
|
|
|
|
*/
|
|
|
|
if ((cl & 1) == 0) {
|
|
|
|
nextcl |= ((p[1] & 0xf0) << 8);
|
|
|
|
} else {
|
|
|
|
nextcl <<= 4;
|
|
|
|
nextcl |= (p[0] & 0x0f);
|
|
|
|
}
|
|
|
|
|
|
|
|
le16enc(p, (uint16_t)nextcl);
|
|
|
|
|
|
|
|
return (0);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* FAT16 accessors.
|
|
|
|
*
|
|
|
|
* FAT16s are sufficiently small, expect it to always fit in the RAM.
|
|
|
|
*/
|
|
|
|
static inline uint8_t *
|
|
|
|
fat_get_fat16_ptr(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
return (fat->fatbuf + (cl << 1));
|
|
|
|
}
|
|
|
|
|
|
|
|
static cl_t
|
|
|
|
fat_get_fat16_next(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
const uint8_t *p;
|
|
|
|
cl_t retval;
|
|
|
|
|
|
|
|
p = fat_get_fat16_ptr(fat, cl);
|
|
|
|
retval = le16dec(p) & CLUST16_MASK;
|
|
|
|
|
|
|
|
if (retval >= (CLUST_BAD & CLUST16_MASK))
|
|
|
|
retval |= ~CLUST16_MASK;
|
|
|
|
|
|
|
|
return (retval);
|
|
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
|
|
fat_set_fat16_next(struct fat_descriptor *fat, cl_t cl, cl_t nextcl)
|
|
|
|
{
|
|
|
|
uint8_t *p;
|
|
|
|
|
|
|
|
/* Truncate 'nextcl' value, if needed */
|
|
|
|
nextcl &= CLUST16_MASK;
|
|
|
|
|
|
|
|
p = fat_get_fat16_ptr(fat, cl);
|
|
|
|
|
|
|
|
le16enc(p, (uint16_t)nextcl);
|
|
|
|
|
|
|
|
return (0);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* FAT32 accessors.
|
|
|
|
*/
|
|
|
|
static inline uint8_t *
|
|
|
|
fat_get_fat32_ptr(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
return (fat->fatbuf + (cl << 2));
|
|
|
|
}
|
|
|
|
|
|
|
|
static cl_t
|
|
|
|
fat_get_fat32_next(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
const uint8_t *p;
|
|
|
|
cl_t retval;
|
|
|
|
|
|
|
|
p = fat_get_fat32_ptr(fat, cl);
|
|
|
|
retval = le32dec(p) & CLUST32_MASK;
|
|
|
|
|
|
|
|
if (retval >= (CLUST_BAD & CLUST32_MASK))
|
|
|
|
retval |= ~CLUST32_MASK;
|
|
|
|
|
|
|
|
return (retval);
|
|
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
|
|
fat_set_fat32_next(struct fat_descriptor *fat, cl_t cl, cl_t nextcl)
|
|
|
|
{
|
|
|
|
uint8_t *p;
|
|
|
|
|
|
|
|
/* Truncate 'nextcl' value, if needed */
|
|
|
|
nextcl &= CLUST32_MASK;
|
|
|
|
|
|
|
|
p = fat_get_fat32_ptr(fat, cl);
|
|
|
|
|
|
|
|
le32enc(p, (uint32_t)nextcl);
|
|
|
|
|
|
|
|
return (0);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline size_t
|
|
|
|
fat_get_iosize(struct fat_descriptor *fat, off_t address)
|
|
|
|
{
|
|
|
|
|
|
|
|
if (address == fat->fat32_lastaddr) {
|
|
|
|
return (fat->fatsize & ((off_t)fat32_cache_chunk_size - 1));
|
|
|
|
} else {
|
|
|
|
return (fat32_cache_chunk_size);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
|
|
fat_flush_fat32_cache_entry(struct fat_descriptor *fat,
|
|
|
|
struct fat32_cache_entry *entry)
|
|
|
|
{
|
|
|
|
int fd;
|
|
|
|
off_t fat_addr;
|
|
|
|
size_t writesize;
|
|
|
|
|
|
|
|
fd = fd_of_(fat);
|
|
|
|
|
|
|
|
if (!entry->dirty)
|
|
|
|
return (FSOK);
|
|
|
|
|
|
|
|
writesize = fat_get_iosize(fat, entry->addr);
|
|
|
|
|
|
|
|
fat_addr = fat->fat32_offset + entry->addr;
|
|
|
|
if (lseek(fd, fat_addr, SEEK_SET) != fat_addr ||
|
|
|
|
(size_t)write(fd, entry->chunk, writesize) != writesize) {
|
|
|
|
pfatal("Unable to write FAT");
|
|
|
|
return (FSFATAL);
|
|
|
|
}
|
|
|
|
|
|
|
|
entry->dirty = false;
|
|
|
|
return (FSOK);
|
|
|
|
}
|
|
|
|
|
|
|
|
static struct fat32_cache_entry *
|
|
|
|
fat_get_fat32_cache_entry(struct fat_descriptor *fat, off_t addr,
|
|
|
|
bool writing)
|
|
|
|
{
|
|
|
|
int fd;
|
|
|
|
struct fat32_cache_entry *entry, *first;
|
|
|
|
off_t fat_addr;
|
|
|
|
size_t rwsize;
|
|
|
|
|
|
|
|
addr &= ~(fat32_cache_chunk_size - 1);
|
|
|
|
|
|
|
|
first = TAILQ_FIRST(&fat->fat32_cache_head);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Cache hit: if we already have the chunk, move it to list head
|
|
|
|
*/
|
|
|
|
TAILQ_FOREACH(entry, &fat->fat32_cache_head, entries) {
|
|
|
|
if (entry->addr == addr) {
|
|
|
|
if (writing) {
|
|
|
|
entry->dirty = true;
|
|
|
|
}
|
|
|
|
if (entry != first) {
|
|
|
|
|
|
|
|
TAILQ_REMOVE(&fat->fat32_cache_head, entry, entries);
|
|
|
|
TAILQ_INSERT_HEAD(&fat->fat32_cache_head, entry, entries);
|
|
|
|
}
|
|
|
|
return (entry);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Cache miss: detach the chunk at tail of list, overwrite with
|
|
|
|
* the located chunk, and populate with data from disk.
|
|
|
|
*/
|
|
|
|
entry = TAILQ_LAST(&fat->fat32_cache_head, cachehead);
|
|
|
|
TAILQ_REMOVE(&fat->fat32_cache_head, entry, entries);
|
|
|
|
if (fat_flush_fat32_cache_entry(fat, entry) != FSOK) {
|
|
|
|
return (NULL);
|
|
|
|
}
|
|
|
|
|
|
|
|
rwsize = fat_get_iosize(fat, addr);
|
|
|
|
fat_addr = fat->fat32_offset + addr;
|
|
|
|
entry->addr = addr;
|
|
|
|
fd = fd_of_(fat);
|
|
|
|
if (lseek(fd, fat_addr, SEEK_SET) != fat_addr ||
|
|
|
|
(size_t)read(fd, entry->chunk, rwsize) != rwsize) {
|
|
|
|
pfatal("Unable to read FAT");
|
|
|
|
return (NULL);
|
|
|
|
}
|
|
|
|
if (writing) {
|
|
|
|
entry->dirty = true;
|
|
|
|
}
|
|
|
|
TAILQ_INSERT_HEAD(&fat->fat32_cache_head, entry, entries);
|
|
|
|
|
|
|
|
return (entry);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline uint8_t *
|
|
|
|
fat_get_fat32_cached_ptr(struct fat_descriptor *fat, cl_t cl, bool writing)
|
|
|
|
{
|
|
|
|
off_t addr, off;
|
|
|
|
struct fat32_cache_entry *entry;
|
|
|
|
|
|
|
|
addr = cl << 2;
|
|
|
|
entry = fat_get_fat32_cache_entry(fat, addr, writing);
|
|
|
|
|
|
|
|
if (entry != NULL) {
|
|
|
|
off = addr & (fat32_cache_chunk_size - 1);
|
|
|
|
return (entry->chunk + off);
|
|
|
|
} else {
|
|
|
|
return (NULL);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
static cl_t
|
|
|
|
fat_get_fat32_cached_next(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
const uint8_t *p;
|
|
|
|
cl_t retval;
|
|
|
|
|
|
|
|
p = fat_get_fat32_cached_ptr(fat, cl, false);
|
|
|
|
if (p != NULL) {
|
|
|
|
retval = le32dec(p) & CLUST32_MASK;
|
|
|
|
if (retval >= (CLUST_BAD & CLUST32_MASK))
|
|
|
|
retval |= ~CLUST32_MASK;
|
|
|
|
} else {
|
|
|
|
retval = CLUST_DEAD;
|
|
|
|
}
|
|
|
|
|
|
|
|
return (retval);
|
|
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
|
|
fat_set_fat32_cached_next(struct fat_descriptor *fat, cl_t cl, cl_t nextcl)
|
|
|
|
{
|
|
|
|
uint8_t *p;
|
|
|
|
|
|
|
|
/* Truncate 'nextcl' value, if needed */
|
|
|
|
nextcl &= CLUST32_MASK;
|
|
|
|
|
|
|
|
p = fat_get_fat32_cached_ptr(fat, cl, true);
|
|
|
|
if (p != NULL) {
|
|
|
|
le32enc(p, (uint32_t)nextcl);
|
|
|
|
return FSOK;
|
|
|
|
} else {
|
|
|
|
return FSFATAL;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
cl_t fat_get_cl_next(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
|
|
|
|
if (!valid_cl(fat, cl)) {
|
|
|
|
pfatal("Invalid cluster: %ud", cl);
|
|
|
|
return CLUST_DEAD;
|
|
|
|
}
|
|
|
|
|
|
|
|
return (fat->get(fat, cl));
|
|
|
|
}
|
|
|
|
|
|
|
|
int fat_set_cl_next(struct fat_descriptor *fat, cl_t cl, cl_t nextcl)
|
|
|
|
{
|
|
|
|
|
|
|
|
if (rdonly) {
|
|
|
|
pwarn(" (NO WRITE)\n");
|
|
|
|
return FSFATAL;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (!valid_cl(fat, cl)) {
|
|
|
|
pfatal("Invalid cluster: %ud", cl);
|
|
|
|
return FSFATAL;
|
|
|
|
}
|
|
|
|
|
|
|
|
return (fat->set(fat, cl, nextcl));
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline struct bootblock*
|
|
|
|
boot_of_(struct fat_descriptor *fat) {
|
|
|
|
|
|
|
|
return (fat->boot);
|
|
|
|
}
|
|
|
|
|
|
|
|
struct bootblock*
|
|
|
|
fat_get_boot(struct fat_descriptor *fat) {
|
|
|
|
|
|
|
|
return (boot_of_(fat));
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline int
|
|
|
|
fd_of_(struct fat_descriptor *fat)
|
|
|
|
{
|
|
|
|
return (fat->fd);
|
|
|
|
}
|
|
|
|
|
|
|
|
int
|
|
|
|
fat_get_fd(struct fat_descriptor * fat)
|
|
|
|
{
|
|
|
|
return (fd_of_(fat));
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Whether a cl is in valid data range.
|
|
|
|
*/
|
|
|
|
bool
|
|
|
|
fat_is_valid_cl(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
|
|
|
|
return (valid_cl(fat, cl));
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline bool
|
|
|
|
valid_cl(struct fat_descriptor *fat, cl_t cl)
|
|
|
|
{
|
|
|
|
const struct bootblock *boot = boot_of_(fat);
|
|
|
|
|
|
|
|
return (cl >= CLUST_FIRST && cl < boot->NumClusters);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
2004-02-05 06:55:12 +00:00
|
|
|
* The first 2 FAT entries contain pseudo-cluster numbers with the following
|
|
|
|
* layout:
|
|
|
|
*
|
|
|
|
* 31...... ........ ........ .......0
|
|
|
|
* rrrr1111 11111111 11111111 mmmmmmmm FAT32 entry 0
|
|
|
|
* rrrrsh11 11111111 11111111 11111xxx FAT32 entry 1
|
2019-08-19 05:24:42 +00:00
|
|
|
*
|
2004-02-05 06:55:12 +00:00
|
|
|
* 11111111 mmmmmmmm FAT16 entry 0
|
|
|
|
* sh111111 11111xxx FAT16 entry 1
|
2019-08-19 05:24:42 +00:00
|
|
|
*
|
2004-02-05 06:55:12 +00:00
|
|
|
* r = reserved
|
|
|
|
* m = BPB media ID byte
|
|
|
|
* s = clean flag (1 = dismounted; 0 = still mounted)
|
|
|
|
* h = hard error flag (1 = ok; 0 = I/O error)
|
|
|
|
* x = any value ok
|
|
|
|
*/
|
|
|
|
|
2004-02-05 06:32:16 +00:00
|
|
|
int
|
|
|
|
checkdirty(int fs, struct bootblock *boot)
|
|
|
|
{
|
|
|
|
off_t off;
|
|
|
|
u_char *buffer;
|
|
|
|
int ret = 0;
|
2012-10-21 12:01:11 +00:00
|
|
|
size_t len;
|
2004-02-05 06:32:16 +00:00
|
|
|
|
Fixed some bugs in checkdirty(). The check for the clean bit was
combined with the the signature check in a wrong way (basically
(dirty:= signature_recognised() && !clean) instead of
(mightbedirty:= !signature_recognized || !clean), so file systems
with unrecognized signatures were considered clean. Many of the
don't-care and reserved bits were not ignored, so some file systems
with valid signatures were unrecognized. One of my FAT32 file systems
has a signature of f8,ff,ff,ff,ff,ff,ff,f7 when dirty, but only
f8,ff,ff,0f,ff,ff,ff,07 was recognised as dirty for FAT32, so the
fail-unsafeness made my file system always considered clean.
Check the i/o non-error bit in checkdirty(). Its absence would give
an unrecognized signature in code that is unaware of it, but we now
mask it out of the signature so we have to check it explicitly. This
combines naturally with the check of the clean bit.
Reviewed by: rnordier (except for final details)
2004-02-05 15:18:18 +00:00
|
|
|
if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
|
2004-02-05 06:32:16 +00:00
|
|
|
return 0;
|
|
|
|
|
2010-02-14 12:31:28 +00:00
|
|
|
off = boot->bpbResSectors;
|
|
|
|
off *= boot->bpbBytesPerSec;
|
2004-02-05 06:32:16 +00:00
|
|
|
|
2012-10-21 12:01:11 +00:00
|
|
|
buffer = malloc(len = boot->bpbBytesPerSec);
|
2004-02-05 06:32:16 +00:00
|
|
|
if (buffer == NULL) {
|
2012-10-21 12:01:11 +00:00
|
|
|
perr("No space for FAT sectors (%zu)", len);
|
2004-02-05 06:32:16 +00:00
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (lseek(fs, off, SEEK_SET) != off) {
|
2012-10-21 12:01:11 +00:00
|
|
|
perr("Unable to read FAT");
|
2004-02-05 06:32:16 +00:00
|
|
|
goto err;
|
|
|
|
}
|
|
|
|
|
2010-06-20 09:40:54 +00:00
|
|
|
if ((size_t)read(fs, buffer, boot->bpbBytesPerSec) !=
|
|
|
|
boot->bpbBytesPerSec) {
|
2012-10-21 12:01:11 +00:00
|
|
|
perr("Unable to read FAT");
|
2004-02-05 06:32:16 +00:00
|
|
|
goto err;
|
|
|
|
}
|
|
|
|
|
Fixed some bugs in checkdirty(). The check for the clean bit was
combined with the the signature check in a wrong way (basically
(dirty:= signature_recognised() && !clean) instead of
(mightbedirty:= !signature_recognized || !clean), so file systems
with unrecognized signatures were considered clean. Many of the
don't-care and reserved bits were not ignored, so some file systems
with valid signatures were unrecognized. One of my FAT32 file systems
has a signature of f8,ff,ff,ff,ff,ff,ff,f7 when dirty, but only
f8,ff,ff,0f,ff,ff,ff,07 was recognised as dirty for FAT32, so the
fail-unsafeness made my file system always considered clean.
Check the i/o non-error bit in checkdirty(). Its absence would give
an unrecognized signature in code that is unaware of it, but we now
mask it out of the signature so we have to check it explicitly. This
combines naturally with the check of the clean bit.
Reviewed by: rnordier (except for final details)
2004-02-05 15:18:18 +00:00
|
|
|
/*
|
|
|
|
* If we don't understand the FAT, then the file system must be
|
|
|
|
* assumed to be unclean.
|
|
|
|
*/
|
2010-02-14 12:31:28 +00:00
|
|
|
if (buffer[0] != boot->bpbMedia || buffer[1] != 0xff)
|
Fixed some bugs in checkdirty(). The check for the clean bit was
combined with the the signature check in a wrong way (basically
(dirty:= signature_recognised() && !clean) instead of
(mightbedirty:= !signature_recognized || !clean), so file systems
with unrecognized signatures were considered clean. Many of the
don't-care and reserved bits were not ignored, so some file systems
with valid signatures were unrecognized. One of my FAT32 file systems
has a signature of f8,ff,ff,ff,ff,ff,ff,f7 when dirty, but only
f8,ff,ff,0f,ff,ff,ff,07 was recognised as dirty for FAT32, so the
fail-unsafeness made my file system always considered clean.
Check the i/o non-error bit in checkdirty(). Its absence would give
an unrecognized signature in code that is unaware of it, but we now
mask it out of the signature so we have to check it explicitly. This
combines naturally with the check of the clean bit.
Reviewed by: rnordier (except for final details)
2004-02-05 15:18:18 +00:00
|
|
|
goto err;
|
|
|
|
if (boot->ClustMask == CLUST16_MASK) {
|
|
|
|
if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f)
|
|
|
|
goto err;
|
|
|
|
} else {
|
|
|
|
if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f
|
|
|
|
|| (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff
|
|
|
|
|| buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03)
|
|
|
|
goto err;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Now check the actual clean flag (and the no-error flag).
|
|
|
|
*/
|
|
|
|
if (boot->ClustMask == CLUST16_MASK) {
|
|
|
|
if ((buffer[3] & 0xc0) == 0xc0)
|
|
|
|
ret = 1;
|
|
|
|
} else {
|
|
|
|
if ((buffer[7] & 0x0c) == 0x0c)
|
|
|
|
ret = 1;
|
|
|
|
}
|
2004-02-05 06:32:16 +00:00
|
|
|
|
|
|
|
err:
|
|
|
|
free(buffer);
|
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
|
2001-07-09 10:35:18 +00:00
|
|
|
/*
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
* Read a FAT from disk. Returns 1 if successful, 0 otherwise.
|
2001-07-09 10:35:18 +00:00
|
|
|
*/
|
|
|
|
static int
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
_readfat(struct fat_descriptor *fat)
|
2001-07-09 10:35:18 +00:00
|
|
|
{
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
int fd;
|
|
|
|
size_t i;
|
|
|
|
off_t off;
|
|
|
|
size_t readsize;
|
|
|
|
struct bootblock *boot;
|
|
|
|
struct fat32_cache_entry *entry;
|
|
|
|
|
|
|
|
boot = boot_of_(fat);
|
|
|
|
fd = fd_of_(fat);
|
|
|
|
fat->fatsize = boot->FATsecs * boot->bpbBytesPerSec;
|
|
|
|
|
|
|
|
off = boot->bpbResSectors;
|
|
|
|
off *= boot->bpbBytesPerSec;
|
|
|
|
|
|
|
|
fat->is_mmapped = false;
|
|
|
|
fat->use_cache = false;
|
|
|
|
|
|
|
|
/* Attempt to mmap() first */
|
|
|
|
if (allow_mmap) {
|
|
|
|
fat->fatbuf = mmap(NULL, fat->fatsize,
|
|
|
|
PROT_READ | (rdonly ? 0 : PROT_WRITE),
|
|
|
|
MAP_SHARED, fd_of_(fat), off);
|
|
|
|
if (fat->fatbuf != MAP_FAILED) {
|
|
|
|
fat->is_mmapped = true;
|
|
|
|
return 1;
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
/*
|
|
|
|
* Unfortunately, we were unable to mmap().
|
|
|
|
*
|
|
|
|
* Only use the cache manager when it's necessary, that is,
|
|
|
|
* when the FAT is sufficiently large; in that case, only
|
|
|
|
* read in the first 4 MiB of FAT into memory, and split the
|
|
|
|
* buffer into chunks and insert to the LRU queue to populate
|
|
|
|
* the cache with data.
|
|
|
|
*/
|
|
|
|
if (boot->ClustMask == CLUST32_MASK &&
|
|
|
|
fat->fatsize >= fat32_cache_size) {
|
|
|
|
readsize = fat32_cache_size;
|
|
|
|
fat->use_cache = true;
|
2001-07-09 10:35:18 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
fat->fat32_offset = boot->bpbResSectors * boot->bpbBytesPerSec;
|
|
|
|
fat->fat32_lastaddr = fat->fatsize & ~(fat32_cache_chunk_size);
|
|
|
|
} else {
|
|
|
|
readsize = fat->fatsize;
|
|
|
|
}
|
|
|
|
fat->fatbuf = malloc(readsize);
|
|
|
|
if (fat->fatbuf == NULL) {
|
|
|
|
perr("No space for FAT (%zu)", readsize);
|
2001-07-09 10:35:18 +00:00
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if (lseek(fd, off, SEEK_SET) != off) {
|
2012-10-21 12:01:11 +00:00
|
|
|
perr("Unable to read FAT");
|
2001-07-09 10:35:18 +00:00
|
|
|
goto err;
|
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if ((size_t)read(fd, fat->fatbuf, readsize) != readsize) {
|
2012-10-21 12:01:11 +00:00
|
|
|
perr("Unable to read FAT");
|
2001-07-09 10:35:18 +00:00
|
|
|
goto err;
|
|
|
|
}
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
/*
|
|
|
|
* When cache is used, split the buffer into chunks, and
|
|
|
|
* connect the buffer into the cache.
|
|
|
|
*/
|
|
|
|
if (fat->use_cache) {
|
|
|
|
TAILQ_INIT(&fat->fat32_cache_head);
|
|
|
|
entry = calloc(fat32_cache_entries, sizeof(*entry));
|
|
|
|
if (entry == NULL) {
|
|
|
|
perr("No space for FAT cache (%zu of %zu)",
|
|
|
|
fat32_cache_entries, sizeof(entry));
|
|
|
|
goto err;
|
|
|
|
}
|
|
|
|
for (i = 0; i < fat32_cache_entries; i++) {
|
|
|
|
entry[i].addr = fat32_cache_chunk_size * i;
|
|
|
|
entry[i].chunk = &fat->fatbuf[entry[i].addr];
|
|
|
|
TAILQ_INSERT_TAIL(&fat->fat32_cache_head,
|
|
|
|
&entry[i], entries);
|
|
|
|
}
|
|
|
|
fat->fat32_cache_allentries = entry;
|
|
|
|
}
|
|
|
|
|
2001-07-09 10:35:18 +00:00
|
|
|
return 1;
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
err:
|
|
|
|
free(fat->fatbuf);
|
|
|
|
fat->fatbuf = NULL;
|
2001-07-09 10:35:18 +00:00
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
static void
|
|
|
|
releasefat(struct fat_descriptor *fat)
|
|
|
|
{
|
|
|
|
if (fat->is_mmapped) {
|
|
|
|
munmap(fat->fatbuf, fat->fatsize);
|
|
|
|
} else {
|
|
|
|
if (fat->use_cache) {
|
|
|
|
free(fat->fat32_cache_allentries);
|
|
|
|
fat->fat32_cache_allentries = NULL;
|
|
|
|
}
|
|
|
|
free(fat->fatbuf);
|
|
|
|
}
|
|
|
|
fat->fatbuf = NULL;
|
|
|
|
bitmap_dtor(&fat->headbitmap);
|
|
|
|
}
|
|
|
|
|
2001-07-09 10:35:18 +00:00
|
|
|
/*
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
* Read or map a FAT and populate head bitmap
|
2001-07-09 10:35:18 +00:00
|
|
|
*/
|
|
|
|
int
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
readfat(int fs, struct bootblock *boot, struct fat_descriptor **fp)
|
2001-07-09 10:35:18 +00:00
|
|
|
{
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
struct fat_descriptor *fat;
|
2001-07-09 10:35:18 +00:00
|
|
|
u_char *buffer, *p;
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
cl_t cl, nextcl;
|
2001-07-09 10:35:18 +00:00
|
|
|
int ret = FSOK;
|
|
|
|
|
|
|
|
boot->NumFree = boot->NumBad = 0;
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
fat = calloc(1, sizeof(struct fat_descriptor));
|
|
|
|
if (fat == NULL) {
|
|
|
|
perr("No space for FAT descriptor");
|
2001-07-09 10:35:18 +00:00
|
|
|
return FSFATAL;
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-01 07:43:08 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
fat->fd = fs;
|
|
|
|
fat->boot = boot;
|
|
|
|
|
|
|
|
if (!_readfat(fat)) {
|
|
|
|
free(fat);
|
|
|
|
return FSFATAL;
|
|
|
|
}
|
|
|
|
buffer = fat->fatbuf;
|
|
|
|
|
|
|
|
/* Populate accessors */
|
|
|
|
switch(boot->ClustMask) {
|
|
|
|
case CLUST12_MASK:
|
|
|
|
fat->get = fat_get_fat12_next;
|
|
|
|
fat->set = fat_set_fat12_next;
|
|
|
|
break;
|
|
|
|
case CLUST16_MASK:
|
|
|
|
fat->get = fat_get_fat16_next;
|
|
|
|
fat->set = fat_set_fat16_next;
|
|
|
|
break;
|
|
|
|
case CLUST32_MASK:
|
|
|
|
if (fat->is_mmapped || !fat->use_cache) {
|
|
|
|
fat->get = fat_get_fat32_next;
|
|
|
|
fat->set = fat_set_fat32_next;
|
|
|
|
} else {
|
|
|
|
fat->get = fat_get_fat32_cached_next;
|
|
|
|
fat->set = fat_set_fat32_cached_next;
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
pfatal("Invalid ClustMask: %d", boot->ClustMask);
|
|
|
|
releasefat(fat);
|
|
|
|
free(fat);
|
|
|
|
return FSFATAL;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (bitmap_ctor(&fat->headbitmap, boot->NumClusters,
|
|
|
|
true) != FSOK) {
|
|
|
|
perr("No space for head bitmap for FAT clusters (%zu)",
|
2019-08-19 05:24:42 +00:00
|
|
|
(size_t)boot->NumClusters);
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
releasefat(fat);
|
|
|
|
free(fat);
|
2001-07-09 10:35:18 +00:00
|
|
|
return FSFATAL;
|
|
|
|
}
|
|
|
|
|
2010-02-14 12:31:28 +00:00
|
|
|
if (buffer[0] != boot->bpbMedia
|
2001-07-09 10:35:18 +00:00
|
|
|
|| buffer[1] != 0xff || buffer[2] != 0xff
|
|
|
|
|| (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
|
|
|
|
|| (boot->ClustMask == CLUST32_MASK
|
|
|
|
&& ((buffer[3]&0x0f) != 0x0f
|
|
|
|
|| buffer[4] != 0xff || buffer[5] != 0xff
|
|
|
|
|| buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
|
|
|
|
|
|
|
|
/* Windows 95 OSR2 (and possibly any later) changes
|
|
|
|
* the FAT signature to 0xXXffff7f for FAT16 and to
|
|
|
|
* 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
|
2002-08-21 18:11:48 +00:00
|
|
|
* file system is dirty if it doesn't reboot cleanly.
|
2001-07-09 10:35:18 +00:00
|
|
|
* Check this special condition before errorring out.
|
|
|
|
*/
|
2010-02-14 12:31:28 +00:00
|
|
|
if (buffer[0] == boot->bpbMedia && buffer[1] == 0xff
|
2001-07-09 10:35:18 +00:00
|
|
|
&& buffer[2] == 0xff
|
|
|
|
&& ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
|
|
|
|
|| (boot->ClustMask == CLUST32_MASK
|
|
|
|
&& buffer[3] == 0x0f && buffer[4] == 0xff
|
|
|
|
&& buffer[5] == 0xff && buffer[6] == 0xff
|
|
|
|
&& buffer[7] == 0x07)))
|
|
|
|
ret |= FSDIRTY;
|
|
|
|
else {
|
|
|
|
/* just some odd byte sequence in FAT */
|
2014-07-14 20:17:09 +00:00
|
|
|
|
2001-07-09 10:35:18 +00:00
|
|
|
switch (boot->ClustMask) {
|
|
|
|
case CLUST32_MASK:
|
|
|
|
pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
|
|
|
|
"FAT starts with odd byte sequence",
|
|
|
|
buffer[0], buffer[1], buffer[2], buffer[3],
|
|
|
|
buffer[4], buffer[5], buffer[6], buffer[7]);
|
|
|
|
break;
|
|
|
|
case CLUST16_MASK:
|
|
|
|
pwarn("%s (%02x%02x%02x%02x)\n",
|
|
|
|
"FAT starts with odd byte sequence",
|
|
|
|
buffer[0], buffer[1], buffer[2], buffer[3]);
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
pwarn("%s (%02x%02x%02x)\n",
|
|
|
|
"FAT starts with odd byte sequence",
|
|
|
|
buffer[0], buffer[1], buffer[2]);
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if (ask(1, "Correct")) {
|
|
|
|
ret |= FSFATMOD;
|
|
|
|
p = buffer;
|
2014-07-14 20:17:09 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
*p++ = (u_char)boot->bpbMedia;
|
|
|
|
*p++ = 0xff;
|
|
|
|
*p++ = 0xff;
|
|
|
|
switch (boot->ClustMask) {
|
|
|
|
case CLUST16_MASK:
|
|
|
|
*p++ = 0xff;
|
|
|
|
break;
|
|
|
|
case CLUST32_MASK:
|
|
|
|
*p++ = 0x0f;
|
|
|
|
*p++ = 0xff;
|
|
|
|
*p++ = 0xff;
|
|
|
|
*p++ = 0xff;
|
|
|
|
*p++ = 0x0f;
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Traverse the FAT table and populate head map. Initially, we
|
|
|
|
* consider all clusters as possible head cluster (beginning of
|
|
|
|
* a file or directory), and traverse the whole allocation table
|
|
|
|
* by marking every non-head nodes as such (detailed below) and
|
|
|
|
* fix obvious issues while we walk.
|
|
|
|
*
|
|
|
|
* For each "next" cluster, the possible values are:
|
|
|
|
*
|
|
|
|
* a) CLUST_FREE or CLUST_BAD. The *current* cluster can't be a
|
|
|
|
* head node.
|
|
|
|
* b) An out-of-range value. The only fix would be to truncate at
|
|
|
|
* the cluster.
|
|
|
|
* c) A valid cluster. It means that cluster (nextcl) is not a
|
|
|
|
* head cluster. Note that during the scan, every cluster is
|
|
|
|
* expected to be seen for at most once, and when we saw them
|
|
|
|
* twice, it means a cross-linked chain which should be
|
|
|
|
* truncated at the current cluster.
|
|
|
|
*
|
|
|
|
* After scan, the remaining set bits indicates all possible
|
|
|
|
* head nodes, because they were never claimed by any other
|
|
|
|
* node as the next node, but we do not know if these chains
|
|
|
|
* would end with a valid EOF marker. We will check that in
|
|
|
|
* checkchain() at a later time when checking directories,
|
|
|
|
* where these head nodes would be marked as non-head.
|
|
|
|
*
|
|
|
|
* In the final pass, all head nodes should be cleared, and if
|
|
|
|
* there is still head nodes, these would be leaders of lost
|
|
|
|
* chain.
|
|
|
|
*/
|
|
|
|
for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
|
|
|
|
nextcl = fat_get_cl_next(fat, cl);
|
|
|
|
|
|
|
|
/* Check if the next cluster number is valid */
|
|
|
|
if (nextcl == CLUST_FREE) {
|
|
|
|
/* Save a hint for next free cluster */
|
|
|
|
if (boot->FSNext == 0) {
|
|
|
|
boot->FSNext = cl;
|
|
|
|
}
|
|
|
|
if (fat_is_cl_head(fat, cl)) {
|
|
|
|
fat_clear_cl_head(fat, cl);
|
|
|
|
}
|
|
|
|
boot->NumFree++;
|
|
|
|
} else if (nextcl == CLUST_BAD) {
|
|
|
|
if (fat_is_cl_head(fat, cl)) {
|
|
|
|
fat_clear_cl_head(fat, cl);
|
|
|
|
}
|
|
|
|
boot->NumBad++;
|
|
|
|
} else if (!valid_cl(fat, nextcl) && nextcl < CLUST_EOFS) {
|
|
|
|
pwarn("Cluster %u continues with %s "
|
|
|
|
"cluster number %u\n",
|
|
|
|
cl, (nextcl < CLUST_RSRVD) ?
|
|
|
|
"out of range" : "reserved",
|
|
|
|
nextcl & boot->ClustMask);
|
|
|
|
if (ask(0, "Truncate")) {
|
|
|
|
ret |= fat_set_cl_next(fat, cl, CLUST_EOF);
|
|
|
|
ret |= FSFATMOD;
|
|
|
|
}
|
|
|
|
} else if (nextcl < boot->NumClusters) {
|
|
|
|
if (fat_is_cl_head(fat, nextcl)) {
|
|
|
|
fat_clear_cl_head(fat, nextcl);
|
|
|
|
} else {
|
|
|
|
pwarn("Cluster %u crossed another chain at %u\n",
|
|
|
|
cl, nextcl);
|
|
|
|
if (ask(0, "Truncate")) {
|
|
|
|
ret |= fat_set_cl_next(fat, cl, CLUST_EOF);
|
|
|
|
ret |= FSFATMOD;
|
|
|
|
}
|
|
|
|
}
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
|
|
|
|
2010-02-14 12:30:30 +00:00
|
|
|
if (ret & FSFATAL) {
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
releasefat(fat);
|
2010-02-14 12:30:30 +00:00
|
|
|
free(fat);
|
|
|
|
*fp = NULL;
|
|
|
|
} else
|
|
|
|
*fp = fat;
|
2001-07-09 10:35:18 +00:00
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Get type of reserved cluster
|
|
|
|
*/
|
2012-10-21 12:01:19 +00:00
|
|
|
const char *
|
2002-03-20 22:57:10 +00:00
|
|
|
rsrvdcltype(cl_t cl)
|
2001-07-09 10:35:18 +00:00
|
|
|
{
|
|
|
|
if (cl == CLUST_FREE)
|
|
|
|
return "free";
|
|
|
|
if (cl < CLUST_BAD)
|
|
|
|
return "reserved";
|
|
|
|
if (cl > CLUST_BAD)
|
|
|
|
return "as EOF";
|
|
|
|
return "bad";
|
|
|
|
}
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
/*
|
|
|
|
* Offer to truncate a chain at the specified CL, called by checkchain().
|
|
|
|
*/
|
|
|
|
static inline int
|
|
|
|
truncate_at(struct fat_descriptor *fat, cl_t current_cl, size_t *chainsize)
|
|
|
|
{
|
|
|
|
int ret = 0;
|
|
|
|
|
|
|
|
if (ask(0, "Truncate")) {
|
|
|
|
ret = fat_set_cl_next(fat, current_cl, CLUST_EOF);
|
|
|
|
(*chainsize)++;
|
|
|
|
return (ret | FSFATMOD);
|
|
|
|
} else {
|
2001-07-09 10:35:18 +00:00
|
|
|
return FSERROR;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
* Examine a cluster chain for errors and count its size.
|
2001-07-09 10:35:18 +00:00
|
|
|
*/
|
|
|
|
int
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
checkchain(struct fat_descriptor *fat, cl_t head, size_t *chainsize)
|
2001-07-09 10:35:18 +00:00
|
|
|
{
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
cl_t current_cl, next_cl;
|
Reduce memory footprint of fsck_msdosfs.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-01 07:43:08 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
/*
|
|
|
|
* We expect that the caller to give us a real, unvisited 'head'
|
|
|
|
* cluster, and it must be a valid cluster. While scanning the
|
|
|
|
* FAT table, we already excluded all clusters that was claimed
|
|
|
|
* as a "next" cluster. Assert all the three conditions.
|
|
|
|
*/
|
|
|
|
assert(valid_cl(fat, head));
|
|
|
|
assert(fat_is_cl_head(fat, head));
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Immediately mark the 'head' cluster that we are about to visit.
|
|
|
|
*/
|
|
|
|
fat_clear_cl_head(fat, head);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* The allocation of a non-zero sized file or directory is
|
|
|
|
* represented as a singly linked list, and the tail node
|
|
|
|
* would be the EOF marker (>=CLUST_EOFS).
|
|
|
|
*
|
|
|
|
* With a valid head node at hand, we expect all subsequent
|
|
|
|
* cluster to be either a not yet seen and valid cluster (we
|
|
|
|
* would continue counting), or the EOF marker (we conclude
|
|
|
|
* the scan of this chain).
|
|
|
|
*
|
|
|
|
* For all other cases, the chain is invalid, and the only
|
|
|
|
* viable fix would be to truncate at the current node (mark
|
|
|
|
* it as EOF) when the next node violates that.
|
|
|
|
*/
|
|
|
|
*chainsize = 0;
|
|
|
|
current_cl = head;
|
|
|
|
for (next_cl = fat_get_cl_next(fat, current_cl);
|
|
|
|
valid_cl(fat, next_cl);
|
|
|
|
current_cl = next_cl, next_cl = fat_get_cl_next(fat, current_cl))
|
|
|
|
(*chainsize)++;
|
|
|
|
|
|
|
|
/* A natural end */
|
|
|
|
if (next_cl >= CLUST_EOFS) {
|
|
|
|
(*chainsize)++;
|
|
|
|
return FSOK;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* The chain ended with an out-of-range cluster number. */
|
|
|
|
pwarn("Cluster %u continues with %s cluster number %u\n",
|
|
|
|
current_cl,
|
|
|
|
next_cl < CLUST_RSRVD ? "out of range" : "reserved",
|
|
|
|
next_cl & boot_of_(fat)->ClustMask);
|
|
|
|
return (truncate_at(fat, current_cl, chainsize));
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
/*
|
|
|
|
* Clear cluster chain from head.
|
|
|
|
*/
|
2001-07-09 10:35:18 +00:00
|
|
|
void
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
clearchain(struct fat_descriptor *fat, cl_t head)
|
2001-07-09 10:35:18 +00:00
|
|
|
{
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
cl_t current_cl, next_cl;
|
|
|
|
struct bootblock *boot = boot_of_(fat);
|
|
|
|
|
|
|
|
current_cl = head;
|
2001-07-09 10:35:18 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
while (valid_cl(fat, current_cl)) {
|
|
|
|
next_cl = fat_get_cl_next(fat, head);
|
|
|
|
(void)fat_set_cl_next(fat, current_cl, CLUST_FREE);
|
|
|
|
boot->NumFree++;
|
|
|
|
current_cl = next_cl;
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
* Overwrite the n-th FAT with FAT0
|
2001-07-09 10:35:18 +00:00
|
|
|
*/
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
static int
|
|
|
|
copyfat(struct fat_descriptor *fat, int n)
|
2001-07-09 10:35:18 +00:00
|
|
|
{
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
size_t rwsize, tailsize, blobs, i;
|
|
|
|
off_t dst_off, src_off;
|
|
|
|
struct bootblock *boot;
|
|
|
|
int ret, fd;
|
2001-07-09 10:35:18 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
ret = FSOK;
|
|
|
|
fd = fd_of_(fat);
|
|
|
|
boot = boot_of_(fat);
|
2001-07-09 10:35:18 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
blobs = howmany(fat->fatsize, fat32_cache_size);
|
|
|
|
tailsize = fat->fatsize % fat32_cache_size;
|
|
|
|
if (tailsize == 0) {
|
|
|
|
tailsize = fat32_cache_size;
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
rwsize = fat32_cache_size;
|
2001-07-09 10:35:18 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
src_off = fat->fat32_offset;
|
|
|
|
dst_off = boot->bpbResSectors + n * boot->FATsecs;
|
|
|
|
dst_off *= boot->bpbBytesPerSec;
|
2001-07-09 10:35:18 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
for (i = 0; i < blobs;
|
|
|
|
i++, src_off += fat32_cache_size, dst_off += fat32_cache_size) {
|
|
|
|
if (i == blobs - 1) {
|
|
|
|
rwsize = tailsize;
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if ((lseek(fd, src_off, SEEK_SET) != src_off ||
|
|
|
|
(size_t)read(fd, fat->fatbuf, rwsize) != rwsize) &&
|
|
|
|
ret == FSOK) {
|
|
|
|
perr("Unable to read FAT0");
|
|
|
|
ret = FSFATAL;
|
|
|
|
continue;
|
2020-01-01 09:22:06 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if ((lseek(fd, dst_off, SEEK_SET) != dst_off ||
|
|
|
|
(size_t)write(fd, fat->fatbuf, rwsize) != rwsize) &&
|
|
|
|
ret == FSOK) {
|
|
|
|
perr("Unable to write FAT %d", n);
|
|
|
|
ret = FSERROR;
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
return (ret);
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
* Write out FAT
|
2001-07-09 10:35:18 +00:00
|
|
|
*/
|
|
|
|
int
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
writefat(struct fat_descriptor *fat)
|
2001-07-09 10:35:18 +00:00
|
|
|
{
|
2010-02-14 12:30:30 +00:00
|
|
|
u_int i;
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
size_t writesz;
|
|
|
|
off_t dst_base;
|
|
|
|
int ret = FSOK, fd;
|
|
|
|
struct bootblock *boot;
|
|
|
|
struct fat32_cache_entry *entry;
|
2001-07-09 10:35:18 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
boot = boot_of_(fat);
|
|
|
|
fd = fd_of_(fat);
|
Reduce memory footprint of fsck_msdosfs.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-01 07:43:08 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if (fat->use_cache) {
|
|
|
|
/*
|
|
|
|
* Attempt to flush all in-flight cache, and bail out
|
|
|
|
* if we encountered an error (but only emit error
|
|
|
|
* message once). Stop proceeding with copyfat()
|
|
|
|
* if any flush failed.
|
|
|
|
*/
|
|
|
|
TAILQ_FOREACH(entry, &fat->fat32_cache_head, entries) {
|
|
|
|
if (fat_flush_fat32_cache_entry(fat, entry) != FSOK) {
|
|
|
|
if (ret == FSOK) {
|
|
|
|
perr("Unable to write FAT");
|
|
|
|
ret = FSFATAL;
|
|
|
|
}
|
|
|
|
}
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if (ret != FSOK)
|
|
|
|
return (ret);
|
2020-01-01 09:22:06 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
/* Update backup copies of FAT, error is not fatal */
|
|
|
|
for (i = 1; i < boot->bpbFATs; i++) {
|
|
|
|
if (copyfat(fat, i) != FSOK)
|
|
|
|
ret = FSERROR;
|
2020-01-01 09:22:06 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
} else {
|
|
|
|
writesz = fat->fatsize;
|
|
|
|
|
|
|
|
for (i = fat->is_mmapped ? 1 : 0; i < boot->bpbFATs; i++) {
|
|
|
|
dst_base = boot->bpbResSectors + i * boot->FATsecs;
|
|
|
|
dst_base *= boot->bpbBytesPerSec;
|
|
|
|
if ((lseek(fd, dst_base, SEEK_SET) != dst_base ||
|
|
|
|
(size_t)write(fd, fat->fatbuf, writesz) != writesz) &&
|
|
|
|
ret == FSOK) {
|
|
|
|
perr("Unable to write FAT %d", i);
|
|
|
|
ret = ((i == 0) ? FSFATAL : FSERROR);
|
|
|
|
}
|
2020-01-01 09:22:06 +00:00
|
|
|
}
|
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
|
2001-07-09 10:35:18 +00:00
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Check a complete in-memory FAT for lost cluster chains
|
|
|
|
*/
|
|
|
|
int
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
checklost(struct fat_descriptor *fat)
|
2001-07-09 10:35:18 +00:00
|
|
|
{
|
|
|
|
cl_t head;
|
|
|
|
int mod = FSOK;
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
int dosfs, ret;
|
|
|
|
size_t chains, chainlength;
|
|
|
|
struct bootblock *boot;
|
|
|
|
|
|
|
|
dosfs = fd_of_(fat);
|
|
|
|
boot = boot_of_(fat);
|
2020-01-01 09:22:06 +00:00
|
|
|
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
/*
|
|
|
|
* At this point, we have already traversed all directories.
|
|
|
|
* All remaining chain heads in the bitmap are heads of lost
|
|
|
|
* chains.
|
|
|
|
*/
|
|
|
|
chains = fat_get_head_count(fat);
|
|
|
|
for (head = CLUST_FIRST;
|
|
|
|
chains > 0 && head < boot->NumClusters;
|
|
|
|
) {
|
|
|
|
/*
|
|
|
|
* We expect the bitmap to be very sparse, so skip if
|
|
|
|
* the range is full of 0's
|
|
|
|
*/
|
|
|
|
if (head % LONG_BIT == 0 &&
|
|
|
|
!fat_is_cl_head_in_range(fat, head)) {
|
|
|
|
head += LONG_BIT;
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
if (fat_is_cl_head(fat, head)) {
|
|
|
|
ret = checkchain(fat, head, &chainlength);
|
|
|
|
if (ret != FSERROR) {
|
|
|
|
pwarn("Lost cluster chain at cluster %u\n"
|
|
|
|
"%zd Cluster(s) lost\n",
|
|
|
|
head, chainlength);
|
|
|
|
mod |= ret = reconnect(fat, head,
|
|
|
|
chainlength);
|
|
|
|
}
|
|
|
|
if (mod & FSFATAL)
|
|
|
|
break;
|
|
|
|
if (ret == FSERROR && ask(0, "Clear")) {
|
|
|
|
clearchain(fat, head);
|
|
|
|
mod |= FSFATMOD;
|
|
|
|
}
|
|
|
|
chains--;
|
Reduce memory footprint of fsck_msdosfs.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-01 07:43:08 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
head++;
|
2001-07-09 10:35:18 +00:00
|
|
|
}
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
|
2001-07-09 10:35:18 +00:00
|
|
|
finishlf();
|
|
|
|
|
2010-02-14 12:31:28 +00:00
|
|
|
if (boot->bpbFSInfo) {
|
2001-07-09 10:35:18 +00:00
|
|
|
ret = 0;
|
2014-07-14 20:17:09 +00:00
|
|
|
if (boot->FSFree != 0xffffffffU &&
|
|
|
|
boot->FSFree != boot->NumFree) {
|
|
|
|
pwarn("Free space in FSInfo block (%u) not correct (%u)\n",
|
2001-07-09 10:35:18 +00:00
|
|
|
boot->FSFree, boot->NumFree);
|
2008-01-31 13:16:29 +00:00
|
|
|
if (ask(1, "Fix")) {
|
2001-07-09 10:35:18 +00:00
|
|
|
boot->FSFree = boot->NumFree;
|
|
|
|
ret = 1;
|
|
|
|
}
|
|
|
|
}
|
2019-04-04 23:16:36 +00:00
|
|
|
if (boot->FSNext != 0xffffffffU &&
|
|
|
|
(boot->FSNext >= boot->NumClusters ||
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
(boot->NumFree && fat_get_cl_next(fat, boot->FSNext) != CLUST_FREE))) {
|
2019-04-04 23:16:36 +00:00
|
|
|
pwarn("Next free cluster in FSInfo block (%u) %s\n",
|
|
|
|
boot->FSNext,
|
|
|
|
(boot->FSNext >= boot->NumClusters) ? "invalid" : "not free");
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if (ask(1, "Fix"))
|
2019-04-04 23:16:36 +00:00
|
|
|
for (head = CLUST_FIRST; head < boot->NumClusters; head++)
|
Reduce memory footprint of fsck_msdosfs.
This is a re-apply r356249 with changes to make GCC happy.
This utility was initially written for FAT12/16, which were inherently
small. When FAT32 support was added, the old data structure and
algorithms remain used with minimal changes.
With growing size of FAT32 media, the current data structure that
requires 4 32-bit variables per each FAT32 table entry would consume up
to 4 GiB of RAM, which can be too big for systems with limited RAM
available.
Address this by taking a different approach of validating the FAT.
The FAT is essentially a set of linked lists of chains that was
referenced by directory entries, and the checker needs to make sure that
the linked chains of clusters do not have cross-linked chains, and every
chain were referenced by one and only one directory entry. Instead of
keeping track of the chain's 'head' cluster number, the size of the
chain, the used status of the chain and the "next" pointer which is
content of the FAT table, we create accessors for the FAT table data
for the "next" pointer, and keep only one bit to indicate if the
current cluster is a 'head' node of a cluster chain, in a bitmap.
We further overhaul the FAT checker to find out the possible head nodes
by excluding ones that are not (in other words, nodes that have some
other nodes claiming them as the next node) instead of marking the head
nodes for each node on the chain. This approach greatly reduced the
complexiety of computation from O(N^2) worst case, to an O(N) scan for
worst case. The file (cluster chain) length is not useful for the FAT
checker, so don't bother to calculate them in the FAT checker and
instead leave the task to the directory structure check, at which point
we would have non-crossed cluster chains, and we are guaranteed that
each cluster will be visited for at most one time.
When checking the directory structures, we use the head node indicator
to as the visited (used) flag: every cluster chain can only be
referenced by one directory entry, so we clear them when calculating
the length of the chain, and we can immediately tell if there are
anomalies in the directory entry.
As a result, the required RAM size is now 1 bit per each entry of
the FAT table, plus memory needed to hold the FAT table in memory,
instead of 16 bytes (=128 bits) per each entry. For FAT12 and FAT16,
we will load the whole FAT table into memory as they are smaller than
128KiB, and for FAT32, we first attempt to mmap() it into memory, and
when that fails, we would fall back to a simple LRU cache of 4 MiB of
RAM.
sbin/fsck_msdosfs/boot.c:
- Added additional sanity checks for valid FAT32/FAT16/FAT12 cluster
number.
- FAT32: check if root directory starts with a valid cluster number,
moved from dir.c. There is no point to proceed if the filesystem
is already damaged beyond repair.
sbin/fsck_msdosfs/check.c:
- Combine phase 1 and phase 2, now that the readfat() is able to
detect cross chains.
sbin/fsck_msdosfs/dir.c:
- Refactor code to use FAT accessor instead of accessing the internal
representation of FAT table.
- Make use of the cluster chain head bitmap.
- Clarify and simplify directory entry check, remove unnecessary
checks that are would be done at a later time (for example, whether
the directory's second cluster is a valid one, which is examined
more throughly in a later checkchain() and does not prevent us
from proceeding further).
sbin/fsck_msdosfs/dosfs.h:
- Remove internal representation of FAT table, which is replaced by
the head bitmap that is opaque to other code.
- Added a special CLUST_DEAD cluster type to indicate errors.
sbin/fsck_msdosfs/ext.h:
- Added a flag that overrides mmap(2) setting. The corresponding
command line option, -M is intentionally undocumented as we do not
expect users to need it.
- Added accessors for FAT table and convert existing interface to use
it.
sbin/fsck_msdosfs/fat.c:
- Added head bitmap to represent whether a cluster is a head cluster.
- Converted FAT internal representation to accessors.
- Implemented a LRU cache for FAT32 when mmap(2) should not or can not
be used.
- _readfat: Attempt a mmap(2) and fall back to regular read for
non-FAT32 file systems; use the LRU cache for FAT32 and prepopulate
the cache with the first 4MiB of the entries.
- readfat: Added support of head bitmap and use the population scan to
detect bogus chains.
- clusterdiff: removed, FATs are copied from the checked copy via
writefat()/copyfat().
- checkchain: calculates the length of a cluster chain and make sure
that it ends with a valid EOF marker.
- clearchain: follow and clear a chain and maintain the free cluster
count.
- checklost: convert to use head bitmap. At the end of all other scans,
the remaining 'head' nodes are leaders of lost cluster chains.
sbin/fsck_msdosfs/fat.c:
- Added a new -M option which is intentionally undocumented, to disable
the use of mmap().
Reviewed by: kevlo
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D22965
2020-01-03 00:31:48 +00:00
|
|
|
if (fat_get_cl_next(fat, head) == CLUST_FREE) {
|
2019-04-04 23:16:36 +00:00
|
|
|
boot->FSNext = head;
|
|
|
|
ret = 1;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
2001-07-09 10:35:18 +00:00
|
|
|
if (ret)
|
|
|
|
mod |= writefsinfo(dosfs, boot);
|
|
|
|
}
|
|
|
|
|
|
|
|
return mod;
|
|
|
|
}
|