and it is no longer referenced by a user process. The inode for a
file whose name has been removed, but is still referenced at the
time of a crash will still be allocated in the filesystem, but will
have no references (e.g., they will have no names referencing them
from any directory).
With traditional soft updates these unreferenced inodes will be
found and reclaimed when the background fsck is run. When using
journaled soft updates, the kernel must keep track of these inodes
so that it can find and reclaim them during the cleanup process.
Their existence cannot be stored in the journal as the journal only
handles short-term events, and they may persist for days. So, they
are tracked by keeping them in a linked list whose head pointer is
stored in the superblock. The journal tracks them only until their
linked list pointers have been commited to disk. Part of the cleanup
process involves traversing the list of unreferenced inodes and
reclaiming them.
This bug was triggered when confusion arose in the commit steps
of keeping the unreferenced-inode linked list coherent on disk.
Notably, a race between the link() system call adding a link-count
to a file and the unlink() system call removing a link-count to
the file. Here if the unlink() ran after link() had looked up
the file but before link() had incremented the link-count of the
file, the file's link-count would drop to zero before the link()
incremented it back up to one. If the file was referenced by a
user process, the first transition through zero made it appear
that it should be added to the unreferenced-inode list when in
fact it should not have been added. If the new name created by
link() was deleted within a few seconds (with the file still
referenced by a user process) it would legitimately be a candidate
for addition to the unreferenced-inode list. The result was that
there were two attempts to add the same inode to the unreferenced-inode
list which scrambled the unreferenced-inode list's pointers leading
to a panic. The fix is to detect and avoid the false attempt at
adding it to the unreferenced-inode list by having the link()
system call check to see if the link count is zero before it
increments it. If it is, the link() fails with ENOENT (showing that
it has failed the link()/unlink() race).
While tracking down this bug, we have added additional assertions
to detect the problem sooner and also simplified some of the code.
Reported by: Kirk Russell
Fix submitted by: Jeff Roberson
Tested by: Peter Holm
PR: kern/159971
MFC (to 9 only): 2 weeks
While we have a snapshot vnode unlocked to avoid a deadlock with another
inode in the same inode block being updated, the filesystem containing
it may be forcibly unmounted. When that happens the snapshot vnode is
revoked. We need to check for that condition and fail appropriately.
This change will be included along with 232351 when it is MFC'ed to 9.
Spotted by: kib
Reviewed by: kib
to enable the collection of counts of synchronous and asynchronous
reads and writes for its associated filesystem. The counts are
displayed using `mount -v'.
Ensure that buffers used for paging indicate the vnode from
which they are operating so that counts of paging I/O operations
from the filesystem are collected.
This checkin only adds the setting of the mount point for the
UFS/FFS filesystem, but it would be trivial to add the setting
and clearing of the mount point at filesystem mount/unmount
time for other filesystems too.
Reviewed by: kib
While there, make some style adjustments, like missed () around
return values.
Submitted by: bde
Reviewed by: mckusick
Tested by: pho
MFC after: 2 weeks
The bawrite() schedules the write to happen immediately, and its use
frees the current thread to do more cleanups.
Submitted by: bde
Reviewed by: mckusick
Tested by: pho
MFC after: 2 weeks
Synchronous inode block update is not needed for MNT_LAZY callers (syncer),
and since waitfor values are not zero, code did unneccessary synchronous
update.
Submitted by: bde
Reviewed by: mckusick
Tested by: pho
MFC after: 2 weeks
snapshots on UFS filesystems running with journaled soft updates.
This is the first of several bugs that need to be fixed before
removing the restriction added in -r230250 to prevent the use
of snapshots on filesystems running with journaled soft updates.
The deadlock occurs when holding the snapshot lock (snaplk)
and then trying to flush an inode via ffs_update(). We become
blocked by another process trying to flush a different inode
contained in the same inode block that we need. It holds the
inode block for which we are waiting locked. When it tries to
write the inode block, it gets blocked waiting for the our
snaplk when it calls ffs_copyonwrite() to see if the inode
block needs to be copied in our snapshot.
The most obvious place that this deadlock arises is in the
ffs_copyonwrite() routine when it updates critical metadata
in a snapshot and tries to write it out before proceeding.
The fix here is to write the data and indirect block pointer
for the snapshot, but to skip the call to ffs_update() to
write the snapshot inode. To ensure that we will never have
to update a pointer in the inode itself, the ffs_snapshot()
routine that creates the snapshot has to ensure that all the
direct blocks are allocated as part of the creation of the
snapshot.
A less obvious place that this deadlock occurs is when we hold
the snaplk because we are deleting a snapshot. In the course of
doing the deletion, we need to allocate various soft update
dependency structures and allocate some journal space. If we
hit a resource limit while doing this we decrease the resources
in use by flushing out an existing dirty file to get it to give
up the soft dependency resources that it holds. The flush can
cause an ffs_update() to be done on the inode for the file that
we have selected to flush resulting in the same deadlock as
described above when the inode that we have chosen to flush
resides in the same inode block as the snapshot inode that we hold.
The fix is to defer cleaning up any time that the inode on which
we are operating is a snapshot.
Help and review by: Jeff Roberson
Tested by: Peter Holm
MFC (to 9 only) after: 2 weeks
Add the sysctl debug.iosize_max_clamp, enabled by default. Setting the
sysctl to zero allows to perform the SSIZE_MAX-sized i/o requests from
the usermode.
Discussed with: bde, das (previous versions)
MFC after: 1 month
the kernel allocated a buffer but did not zero it as it was about
to be completely filled by a uiomove() from the user's buffer.
However, if the uiomove() failed, the old contents of the buffer
could be exposed especially if the file was being mmap'ed. The
fix was to always zero the buffer when it was allocated.
This change first attempts the uiomove() to the newly allocated
(and dirty) buffer and only zeros it if the uiomove() fails. The
effect is to eliminate the gratuitous zeroing of the buffer in
the usual case where the uiomove() successfully fills it.
Reviewed by: kib
Tested by: scottl
MFC after: 2 weeks (to 9 only)
every 30 seconds. This spike in I/O caused the system to pause every
30 seconds which was quite annoying. So, the way that sync worked
was changed so that when a vnode was first dirtied, it was put on
a 30-second cleaning queue (see the syncer_workitem_pending queues
in kern/vfs_subr.c). If the file has not been written or deleted
after 30 seconds, the syncer pushes it out. As the syncer runs once
per second, dirty files are trickled out slowly over the 30-second
period instead of all at once by a call to sync(2).
The one drawback to this is that it does not cover the filesystem
metadata. To handle the metadata, vfs_allocate_syncvnode() is called
to create a "filesystem syncer vnode" at mount time which cycles
around the cleaning queue being sync'ed every 30 seconds. In the
original design, the only things it would sync for UFS were the
filesystem metadata: inode blocks, cylinder group bitmaps, and the
superblock (e.g., by VOP_FSYNC'ing devvp, the device vnode from
which the filesystem is mounted).
Somewhere in its path to integration with FreeBSD the flushing of
the filesystem syncer vnode got changed to sync every vnode associated
with the filesystem. The result of this change is to return to the
old filesystem-wide flush every 30-seconds behavior and makes the
whole 30-second delay per vnode useless.
This change goes back to the originally intended trickle out sync
behavior. Key to ensuring that all the intended semantics are
preserved (e.g., that all inode updates get flushed within a bounded
period of time) is that all inode modifications get pushed to their
corresponding inode blocks so that the metadata flush by the
filesystem syncer vnode gets them to the disk in a timely way.
Thanks to Konstantin Belousov (kib@) for doing the audit and commit
-r231122 which ensures that all of these updates are being made.
Reviewed by: kib
Tested by: scottl
MFC after: 2 weeks
list. If softdep_sync_buf() discovers such dependency, it should do
nothing, which is safe as it is only waiting on the parent buffer to
be written, so it can be removed.
Committed on behalf of: jeff
MFC after: 1 week
filesystem running with journaled soft updates. Until these problems
have been tracked down, return ENOTSUPP when an attempt is made to
take a snapshot on a filesystem running with journaled soft updates.
MFC after: 2 weeks
vfs_mount_error error message facility provided by the nmount
interface.
Clean up formatting of mount warnings which still need to use
kernel printf's since they do not return errors.
Requested by: Craig Rodrigues <rodrigc@crodrigues.org>
MFC after: 2 weeks
While there, remove a useless check from the code. memcchr() always
returns characters unequal to 0xff in this case, so inosused[i] ^ 0xff
can never be equal to zero. Also, the fact that memcchr() returns a
pointer instead of the number of bytes until the end, makes conversion
to an offset far more easy.
The SYSCTL_NODE macro defines a list that stores all child-elements of
that node. If there's no SYSCTL_DECL macro anywhere else, there's no
reason why it shouldn't be static.
whle tracking down the system hang reported in kern/160662 and
corrected in revision 225806. The LOR is not the cause of the system
hang and indeed cannot cause an actual deadlock. However, it can
be easily eliminated by defering the acquisition of a buflock until
after all the vnode locks have been acquired.
Reported by: Hans Ottevanger
PR: kern/160662
Remove mapped pages for all dataset vnodes in zfs_rezget() using
new vn_pages_remove() to fix mmapped files changed by
zfs rollback or zfs receive -F.
PR: kern/160035, kern/156933
Reviewed by: kib, pjd
Approved by: re (kib)
MFC after: 1 week
(1) opt_capsicum.h is no longer required in ffs_alloc.c, so remove the
#include.
(2) portalfs depends on opt_capsicum.h, so have the Makefile generate one
if required.
These affect only modules built without a kernel (i.e, not buildkernel,
but yes buildworld if the dubious MODULES_WITH_WORLD is used).
Approved by: re (bz)
Sponsored by: Google Inc
kernel for FreeBSD 9.0:
Add a new capability mask argument to fget(9) and friends, allowing system
call code to declare what capabilities are required when an integer file
descriptor is converted into an in-kernel struct file *. With options
CAPABILITIES compiled into the kernel, this enforces capability
protection; without, this change is effectively a no-op.
Some cases require special handling, such as mmap(2), which must preserve
information about the maximum rights at the time of mapping in the memory
map so that they can later be enforced in mprotect(2) -- this is done by
narrowing the rights in the existing max_protection field used for similar
purposes with file permissions.
In namei(9), we assert that the code is not reached from within capability
mode, as we're not yet ready to enforce namespace capabilities there.
This will follow in a later commit.
Update two capability names: CAP_EVENT and CAP_KEVENT become
CAP_POST_KEVENT and CAP_POLL_KEVENT to more accurately indicate what they
represent.
Approved by: re (bz)
Submitted by: jonathan
Sponsored by: Google Inc
so that it is visible to userland programs. This change enables
the `mount' command with no arguments to be able to show if a
filesystem is mounted using journaled soft updates as opposed
to just normal soft updates.
Approved by: re (bz)
(typically fsck_ffs) to register that it wishes to use FFS specific
sysctl's to update the filesystem. This ensures that two checkers
cannot run on a given filesystem at the same time and that no other
process accidentally or maliciously uses the filesystem updating
sysctls inappropriately. This functionality is needed by the
journaling soft-updates recovery code.
flag (FS_SUJ) when determining whether to do journaling-based
operations. The mount flag is set only when journaling is active
while the superblock flag is set to indicate that journaling is to
be used. For example, when the filesystem is mounted read-only, the
journaling may be present (FS_SUJ) but not active (MNTK_SUJ).
Inappropriate checking of the FS_SUJ flag was causing some
journaling actions to be attempted at inappropriate times.
filesystems to be opened for writing. This functionality used to
be special-cased for just the root filesystem, but with this change
is now available for all UFS filesystems. This change is needed for
journaled soft updates recovery.
Discussed with: Jeff Roberson
This will most likely cause new block allocations which can recurse
into request cleanup.
- While here optimize the ufs locking slightly. We need only acquire and
drop once.
- process_removes() and process_truncates() also is only needed once.
- Attempt to flush each item on the worklist once but do not loop forever
if some can not be completed.
Discussed with: mckusick
option to vm_object_page_remove() asserts that the specified range of pages
is not mapped, or more precisely that none of these pages have any managed
mappings. Thus, vm_object_page_remove() need not call pmap_remove_all() on
the pages.
This change not only saves time by eliminating pointless calls to
pmap_remove_all(), but it also eliminates an inconsistency in the use of
pmap_remove_all() versus related functions, like pmap_remove_write(). It
eliminates harmless but pointless calls to pmap_remove_all() that were being
performed on PG_UNMANAGED pages.
Update all of the existing assertions on pmap_remove_all() to reflect this
change.
Reviewed by: kib
and usr.sbin/makefs/ffs/ffs_subr.c as they have no need of anything in that
file. No other programs or libraries include <ufs/ffs/ffs_extern.h> (nor
should they as it is totally in-kernel interfaces). For added protection
I enclosed the entire contents of <ufs/ffs/ffs_extern.h> in ifdef _KERNEL.
Feedback from: Bruce Evans and Tai-hwa Liang
messages for a filesystem being out of space need to be moved so that
they do not print out until after a failed cleanup attempt.
Suggested by: Jeff Roberson
to resolve errors which can cause corruption on recovery with the old
synchronous mechanism.
- Append partial truncation freework structures to indirdeps while
truncation is proceeding. These prevent new block pointers from
becoming valid until truncation completes and serialize truncations.
- On completion of a partial truncate journal work waits for zeroed
pointers to hit indirects.
- softdep_journal_freeblocks() handles last frag allocation and last
block zeroing.
- vtruncbuf/ffs_page_remove moved into softdep_*_freeblocks() so it
is only implemented in one place.
- Block allocation failure handling moved up one level so it does not
proceed with buf locks held. This permits us to do more extensive
reclaims when filesystem space is exhausted.
- softdep_sync_metadata() is broken into two parts, the first executes
once at the start of ffs_syncvnode() and flushes truncations and
inode dependencies. The second is called on each locked buf. This
eliminates excessive looping and rollbacks.
- Improve the mechanism in process_worklist_item() that handles
acquiring vnode locks for handle_workitem_remove() so that it works
more generally and does not loop excessively over the same worklist
items on each call.
- Don't corrupt directories by zeroing the tail in fsck. This is only
done for regular files.
- Push a fsync complete record for files that need it so the checker
knows a truncation in the journal is no longer valid.
Discussed with: mckusick, kib (ffs_pages_remove and ffs_truncate parts)
Tested by: pho
Eliminate one (of several) possible conflicting buffer locks when
trying to reclaim blocks. Rest of fix to be incorporated as part
of SUJ update by jeff.
Pointed out by: Kostik Belousov
method, so that callers can indicate the minimum vnode
locking requirement. This will allow some file systems to choose
to return a LK_SHARED locked vnode when LK_SHARED is specified
for the flags argument. This patch only adds the flag. It
does not change any file system to use it and all callers
specify LK_EXCLUSIVE, so file system semantics are not changed.
Reviewed by: kib
should not change. Fetch the td_user_pri under the thread lock. This
is probably not necessary but a magic number also seems preferable to
knowing the implementation details here.
Requested by: Jason Behmer < jason DOT behmer AT isilon DOT com >
goes to zero. E.g., the vnode might be only shared-locked at the time of
vput() call. Such vnodes are kept in the hash, so they can be found later.
If ffs_valloc() allocated an inode that has its vnode cached in hash, and
still owing the inactivation, then vget() call from ffs_valloc() clears
VI_OWEINACT, and then the vnode is reused for the newly allocated inode.
The problem is, the vnode is not reclaimed before it is put to the new
use. ffs_valloc() recycles vnode vm object, but this is not enough.
In particular, at least v_vflag should be cleared, and several bits of
UFS state need to be removed.
It is very inconvenient to call vgone() at this point. Instead, move
some parts of ufs_reclaim() into helper function ufs_prepare_reclaim(),
and call the helper from VOP_RECLAIM and ffs_valloc().
Reviewed by: mckusick
Tested by: pho
MFC after: 3 weeks
for a new journal specific partial truncate routine.
- Use dep_current[] in place of specific dependency counts. This is
automatically maintained when workitems are allocated and has
less risk of becoming incorrect.
- Keep a hash of indirect blocks that have recently been freed and are
still referenced in the journal.
- Lookup blocks in this hash before forcing a new block write to wait on
the journal entry to hit the disk. This is only necessary to avoid
confusion between old identities as indirects and new identities as
file blocks.
- Don't free jseg structures until the journal has written a record that
invalidates it. This keeps the indirect block information around for
as long as is required to be safe.
- Force an empty journal block write when required to flush out stale
journal data that is simply waiting for the oldest valid sequence
number to advance beyond it.
will be removed. Permit the journal to proceed so that we don't leave
a rollback in a cg for a very long time as this can cause terrible perf
problems in low memory situations.
Tested by: pho
up and declaring a filesystem out of space. Especially necessary when
running on a small filesystem. With this improvement, it should be
possible to use soft updates on a small root filesystem.
Kudos to: Peter Holm
Testing by: Peter Holm
MFC: 2 weeks
- In softdep_revert_mkdir() find the dotaddref before we attempt to cancel
the jaddref so we can make assumptions about where the dotaddref is on
the list. cancel_jaddref() does not always remove items from the list
anymore.
- Always set GOINGAWAY on an inode in softdep_freefile() if DEPCOMPLETE
was never set. This ensures that dependencies will continue to be
processed on the inowait/bufwait list and is more an artifact of
the structure of the code than a pure ordering problem.
- Always set DEPCOMPLETE on canceled jaddrefs so that they can be freed
appropriately. This normally occurs when the refs are added to the
journal but if they are canceled before this point the state would
never be set and the dependency could never be freed.
Reported by: pho
Tested by: pho
journal blocks, instead of hard coding 512 byte sector size. Journal need
to atomically write the block, that can only be guaranteed at the device
sector size, not larger. Attempt to write less then sector size results in
driver errors.
Note that this is the first structure in UFS that depends on the
sector size. Other elements are written in the units of fragments.
In collaboration with: pho
Reviewed by: jeff
Tested by: bz, pho
SU+J is not included as a FEATURE macro:
- it was not in the tree during the GSoC
- I do not see an option to en-/disable it in NOTES
Two minor changes where made during the review compared to what was developed
during GSoC 2010.
No FreeBSD version bump, the userland application to query the features will
be committed last and can serve as an indication of the availablility if
needed.
Sponsored by: Google Summer of Code 2010
Submitted by: kibab
Reviewed by: kib
X-MFC after: to be determined in last commit with code from this project
- entirely eliminate some calls to uio_yeild() as being unnecessary,
such as in a sysctl handler.
- move should_yield() and maybe_yield() to kern_synch.c and move the
prototypes from sys/uio.h to sys/proc.h
- add a slightly more generic kern_yield() that can replace the
functionality of uio_yield().
- replace source uses of uio_yield() with the functional equivalent,
or in some cases do not change the thread priority when switching.
- fix a logic inversion bug in vlrureclaim(), pointed out by bde@.
- instead of using the per-cpu last switched ticks, use a per thread
variable for should_yield(). With PREEMPTION, the only reasonable
use of this is to determine if a lock has been held a long time and
relinquish it. Without PREEMPTION, this is essentially the same as
the per-cpu variable.
should_yield(). Use this in various places. Encapsulate the common
case of check-and-yield into a new function maybe_yield().
Change several checks for a magic number of iterations to use
should_yield() instead.
MFC after: 1 week
it at the allocation time for journaled fs and indirect blocks, when
the allocated object is not accessible outside.
Requested and reviewed by: jeff
Tested by: pho
another, deleting it. If the directory is removed, UFS always need to
remove the .. ref, even if the ultimate ref on the parent would not
change. The new directory must have a new journal entry for that ref.
Otherwise journal processing would not properly account for the
parent's reference since it will belong to a removed directory entry.
Change ufs_rename()'s dotdot rename section to always
setup_dotdot_link(). In the tip != NULL case SUJ needs the newref dependency
allocated via setup_dotdot_link().
Stop setting isrmdir to 2 for newdirrem() in softdep_setup_remove().
Remove the isdirrem > 1 checks from newdirrem().
Reported by: many
Submitted by: jeff
Tested by: pho
to the disk, recurse to handle indirect blocks of next level that are
hidden by the corresponding entry.
In collaboration with: pho
Reviewed by: jeff, mckusick
Tested by: mckusick, pho
The FS_TRIM fs flag indicates that administrator requested issuing of
TRIM commands for the volume. UFS will only send the command to disk
if the disk reports GEOM::candelete attribute.
Since disk queue is reordered, data block is marked as free in the bitmap
only after TRIM command completed. Due to need to sleep waiting for
i/o to finish, TRIM bio_done routine schedules taskqueue to set the
bitmap bit.
Based on the patch by: mckusick
Reviewed by: mckusick, pjd
Tested by: pho
MFC after: 1 month
As result, failed softdep_mount() might leave up to two vnodes on the
mp mountlist, preventing mnt_ref from going to zero.
Call ffs_flushfiles() after failed softdep_mount() to clean mountlist.
Initial report by: Garrett Cooper
Reproduced and tested by: pho
deallocate_dependencies() is done. This opens a race between softdep
thread and the thread that does the truncation:
A write of the indirect block causes the freeblks to become
ALLCOMPLETE while softdep_setup_freeblocks() dropped softdep lock. And
then, softdep_disk_write_complete() would reassign the workitem to the
mount point worklist, causing premature processing of the workitem, or
journal write exhaust the fb_jfreeblkhd and handle_written_jfreeblk does
the same reassign.
indir_trunc() then would find the indirect block that is locked (with lock
owned by kernel) but without any dependencies, causing it to hang in
getblk() waiting for buffer lock.
Do not mark freeblks as DEPCOMPLETE until deallocate_dependencies()
finished.
Analyzed, suggested and reviewed by: jeff
Tested by: pho
breakage for old mount(2) syscall, since most struct <filesystem>_args
embed export_args. The mount(2) is supposed to provide ABI
compatibility for pre-nmount mount(8) binaries, so restore ABI to
pre-r184588.
Requested and reviewed by: bde
MFC after: 2 weeks
LK_CANRECURSE after a lock is created. Use them to implement macros that
otherwise manipulated the flags directly. Assert that the associated
lockmgr lock is exclusively locked by the current thread when manipulating
these flags to ensure the flag updates are safe. This last change required
some minor shuffling in a few filesystems to exclusively lock a brand new
vnode slightly earlier.
Reviewed by: kib
MFC after: 3 days
the worklist (in softdep_process_journal), but also after flushing the
workitems. Might be, we should even do this before bwillwrite() too, but
this seems to be not needed for now.
Fs might be suspended during processing the queue, and then there is
nobody around to unsuspend.
In collaboration with: pho
Tested by: bz
Reviewed by: jeff
implementation in 8.0 and later as its flags field does not hold dynamic
state such as waiters flags, but is only modified in lockinit() aside
from VN_LOCK_*().
Discussed with: attilio
changed to defer the setting of VN_LOCK_ASHARE() (which clears LK_NOSHARE
in the vnode lock's flags) until after they had determined if the vnode was
a FIFO. This occurs after the vnode has been inserted a VFS hash or some
similar table, so it is possible for another thread to find this vnode via
vget() on an i-node number and block on the vnode lock. If the lockmgr
interlock (vnode interlock for vnode locks) is not held when clearing the
LK_NOSHARE flag, then the lk_flags field can be clobbered. As a result
the thread blocked on the vnode lock may never get woken up. Fix this by
holding the vnode interlock while modifying the lock flags in this case.
MFC after: 3 days
the context of the process that reduced the effective count. Previously
all truncation as a result of unlink happened in the softdep flush
thread. This had the effect of being impossible to rate limit properly
with the journal code. Now the process issuing unlinks is suspended
when the journal files. This has a side-effect of improving rm
performance by allowing more concurrent work.
- Handle two cases in inactive, one for effnlink == 0 and another when
nlink finally reaches 0.
- Eliminate the SPACECOUNTED related code since the truncation is no
longer delayed.
Discussed with: mckusick
Apparently it's bad when we first have an ANSI prototype in function
declaration, but then use K&R in its defintion.
Complaint from: clang
MFC after: 2 weeks
loader(8)
In r193192 loader(8) has grown an ability to pass root mount options
from fstab via vfs.root.mountfrom.options. Unfortunately, some options
that can be present in fstab are for userland only and lead to root
mounting failure when seen by kernel.
Rather than teaching loader about FFS-specific options that should be
filtered out, ffs_mount recognizes those options as valid, but ignores
and deletes[1] them.
[1] is suggested by jh.
PR: kern/141050
Reported by: many
Reviewed by: jh, bde
MFC after: 4 days
on the last iteration. This can lead to a deadlock when we have
worklist items that cannot be immediately satisfied.
Reported by: uqs, Dimitry Andric <dimitry@andric.com>
- Remove some unnecessary debugging code and place some other under
SUJ_DEBUG.
- Examine the journal state in softdep_slowdown().
- Re-format some comments so I may more easily add flag descriptions.
snapshot code.
- Don't fsync() vnodes in prealloc if copy on write is in progress. It
is not safe to recurse back into the write path here.
Reported by: Vladimir Grebenschikov <vova@fbsd.ru>
successfully made it to the free list yet or not. This fixes
a deadlock that can occur with unlinked but referenced files.
Journal space and inodedeps were not correctly reclaimed because
the inode block was not left dirty.
Tested/Reported by: lwindschuh@googlemail.com
managed pages that didn't already have that lock held. (Freeing an
unmanaged page, such as the various pmaps use, doesn't require the page
lock.)
This allows a change in vm_page_remove()'s locking requirements. It now
expects the page lock to be held instead of the page queues lock.
Consequently, the page queues lock is no longer required at all by callers
to vm_page_rename().
Discussed with: kib
a revert call. In this case don't attempt to remove something that
has not yet been added. Otherwise this jaddref must hang around
to prevent the bitmap write as normal.
brings in support for an optional intent log which eliminates the need
for background fsck on unclean shutdown.
Sponsored by: iXsystems, Yahoo!, and Juniper.
With help from: McKusick and Peter Holm
The assignment is already done in g_vfs_open.
Redundant assignment is harmless, but can become a problem if g_vfs_open
logic is changed.
MFC after: 1 week
pending blocks are scheduled for removal, goes to retry the (re)allocation,
clear the bp pointer. It might happen that meantime free space is really
exhausted and we are entering nospace: label without bread()ing buffer,
causing stale bp value to be brelse()d again.
Tested by: pho
(Producing a scenario to reliably reproduce the
race appeared to be much harder then fixing the bug)
MFC after: 1 week
inode numbers as negative rather than unsigned. For a default
(16K block) file system, this bug began to show up at a file system
size above about 16Tb.
To fully handle this problem, newfs must be updated to ensure that
it will never create a filesystem with more than 2^32 inodes. That
patch will be forthcoming soon.
Reported by: Scott Burns, John Kilburg, Bruce Evans
Followup by: Jeff Roberson
PR: 133980
MFC after: 2 weeks
When renaming a directory it passes through several intermediate
states. First its new name will be created causing it to have two
names (from possibly different parents). Next, if it has different
parents, its value of ".." will be changed from pointing to the old
parent to pointing to the new parent. Concurrently, its old name
will be removed bringing it back into a consistent state. When fsck
encounters an extra name for a directory, it offers to remove the
"extraneous hard link"; when it finds that the names have been
changed but the update to ".." has not happened, it offers to rewrite
".." to point at the correct parent. Both of these changes were
considered unexpected so would cause fsck in preen mode or fsck in
background mode to fail with the need to run fsck manually to fix
these problems. Fsck running in preen mode or background mode now
corrects these expected inconsistencies that arise during directory
rename. The functionality added with this update is used by fsck
running in background mode to make these fixes.
Solution:
This update adds three new fsck sysctl commands to support background
fsck in correcting expected inconsistencies that arise from incomplete
directory rename operations. They are:
setcwd(dirinode) - set the current directory to dirinode in the
filesystem associated with the snapshot.
setdotdot(oldvalue, newvalue) - Verify that the inode number for ".."
in the current directory is oldvalue then change it to newvalue.
unlink(nameptr, oldvalue) - Verify that the inode number associated
with nameptr in the current directory is oldvalue then unlink it.
As with all other fsck sysctls, these new ones may only be used by
processes with appropriate priviledge.
Reported by: jeff
Security issues: rwatson
flag. Besides providing the redundand information, need to update both
vnode and object flags causes more acquisition of vnode interlock.
OBJ_MIGHTBEDIRTY is only checked for vnode-backed vm objects.
Remove VI_OBJDIRTY and make sure that OBJ_MIGHTBEDIRTY is set only for
vnode-backed vm objects.
Suggested and reviewed by: alc
Tested by: pho
MFC after: 3 weeks
dead_vnodeops before calling vgone(). Revert r189706 and corresponding
part of the r186560.
Noted and reviewed by: tegge
Approved by: des (pseudofs part)
MFC after: 3 days
truncate(2) call, or by being removed or truncated on open, either
new softupdate freeblks structure is allocated to track the freed
blocks of the node, or truncation is done syncronously when too many SU
dependencies are accumulated. The decision does not take into account
the allocated freeblks dependencies, allowing workloads that do huge
amount of truncations to exhaust the kernel memory.
Take the number of allocated freeblks into consideration for
softdep_slowdown().
Reported by: pluknet gmail com
Diagnosed and tested by: pho
Approved by: re (rwatson)
MFC after: 1 month
around the sequence that drop vnode lock and then busies the mount point.
Not having vlocked node or direct reference to the mp allows for the
forced unmount to proceed, making mp unmounted or reused.
Tested by: pho
Reviewed by: jeff
Approved by: re (kensmith)
MFC after: 2 weeks
threads to put dirty buffers on the vnode bufobj list. For regular files
and synchronous fsync requests, check for the condition and restart the
fsync vop if a new dirty buffer arrived.
Tested by: pho
Approved by: re (kensmith)
MFC after: 1 month
Use inlined (due to FFSV_FORCEINSMQ) version of vn_vget_ino() to prevent
mountpoint from being unmounted and freed while no vnodes are locked.
Tested by: pho
Approved by: re (kensmith)
MFC after: 1 month
and used in a large number of files, but also because an increasing number
of incorrect uses of MAC calls were sneaking in due to copy-and-paste of
MAC-aware code without the associated opt_mac.h include.
Discussed with: pjd
the VFS. Now all the VFS_* functions and relating parts don't want the
context as long as it always refers to curthread.
In some points, in particular when dealing with VOPs and functions living
in the same namespace (eg. vflush) which still need to be converted,
pass curthread explicitly in order to retain the old behaviour.
Such loose ends will be fixed ASAP.
While here fix a bug: now, UFS_EXTATTR can be compiled alone without the
UFS_EXTATTR_AUTOSTART option.
VFS KPI is heavilly changed by this commit so thirdy parts modules needs
to be recompiled. Bump __FreeBSD_version in order to signal such
situation.
the removal of NQNFS, but was left in in case it was required for NFSv4.
Since our new NFSv4 client and server can't use it for their
requirements, GC the old mechanism, as well as other unused lease-
related code and interfaces.
Due to its impact on kernel programming and binary interfaces, this
change should not be MFC'd.
Proposed by: jeff
Reviewed by: jeff
Discussed with: rmacklem, zach loafman @ isilon
The later may need blocks from the underlying device that belongs
to normal files, that should not be locked while snap lock is held.
Reported and tested by: pho
MFC after: 1 month
the "nbufkv" sleep.
First, ffs background cg group block write requests a new buffer for
the shadow copy. When ffs_bufwrite() is called from the bufdaemon due
to buffers shortage, requesting the buffer deadlock bufdaemon.
Introduce a new flag for getnewbuf(), GB_NOWAIT_BD, to request getblk
to not block while allocating the buffer, and return failure
instead. Add a flag argument to the geteblk to allow to pass the flags
to getblk(). Do not repeat the getnewbuf() call from geteblk if buffer
allocation failed and either GB_NOWAIT_BD is specified, or geteblk()
is called from bufdaemon (or its helper, see below). In
ffs_bufwrite(), fall back to synchronous cg block write if shadow
block allocation failed.
Since r107847, buffer write assumes that vnode owning the buffer is
locked. The second problem is that buffer cache may accumulate many
buffers belonging to limited number of vnodes. With such workload,
quite often threads that own the mentioned vnodes locks are trying to
read another block from the vnodes, and, due to buffer cache
exhaustion, are asking bufdaemon for help. Bufdaemon is unable to make
any substantial progress because the vnodes are locked.
Allow the threads owning vnode locks to help the bufdaemon by doing
the flush pass over the buffer cache before getnewbuf() is going to
uninterruptible sleep. Move the flushing code from buf_daemon() to new
helper function buf_do_flush(), that is called from getnewbuf(). The
number of buffers flushed by single call to buf_do_flush() from
getnewbuf() is limited by new sysctl vfs.flushbufqtarget. Prevent
recursive calls to buf_do_flush() by marking the bufdaemon and threads
that temporarily help bufdaemon by TDP_BUFNEED flag.
In collaboration with: pho
Reviewed by: tegge (previous version)
Tested by: glebius, yandex ...
MFC after: 3 weeks
Provide a custom lock around initializing and tearing down EA area,
to prevent both memory leaks and double-free of it. Count the number
of EA area accessors.
Lock protocol requires either holding exclusive vnode lock to modify
i_ea_area, or shared vnode lock and owning IN_EA_LOCKED flag in i_flag.
Noted by: YAMAMOTO, Taku <taku tackymt homeip net>
Tested by: pho (previous version)
MFC after: 2 weeks
filesystem supports additional operations using shared vnode locks.
Currently this is used to enable shared locks for open() and close() of
read-only file descriptors.
- When an ISOPEN namei() request is performed with LOCKSHARED, use a
shared vnode lock for the leaf vnode only if the mount point has the
extended shared flag set.
- Set LOCKSHARED in vn_open_cred() for requests that specify O_RDONLY but
not O_CREAT.
- Use a shared vnode lock around VOP_CLOSE() if the file was opened with
O_RDONLY and the mountpoint has the extended shared flag set.
- Adjust md(4) to upgrade the vnode lock on the vnode it gets back from
vn_open() since it now may only have a shared vnode lock.
- Don't enable shared vnode locks on FIFO vnodes in ZFS and UFS since
FIFO's require exclusive vnode locks for their open() and close()
routines. (My recent MPSAFE patches for UDF and cd9660 already included
this change.)
- Enable extended shared operations on UFS, cd9660, and UDF.
Submitted by: ups
Reviewed by: pjd (ZFS bits)
MFC after: 1 month
address space sizes to be longs instead of ints. Specifically, the follow
values are now longs: runningbufspace, bufspace, maxbufspace,
bufmallocspace, maxbufmallocspace, lobufspace, hibufspace, lorunningspace,
hirunningspace, maxswzone, maxbcache, and maxpipekva. Previously, a
relatively small number (~ 44000) of buffers set in kern.nbuf would result
in integer overflows resulting either in hangs or bogus values of
hidirtybuffers and lodirtybuffers. Now one has to overflow a long to see
such problems. There was a check for a nbuf setting that would cause
overflows in the auto-tuning of nbuf. I've changed it to always check and
cap nbuf but warn if a user-supplied tunable would cause overflow.
Note that this changes the ABI of several sysctls that are used by things
like top(1), etc., so any MFC would probably require a some gross shims
to allow for that.
MFC after: 1 month
msdosfs_unmount() and ffs_unmount() exit early after getting ENXIO.
However, dounmount() treats ENXIO as a success and proceeds with
unmounting. In effect, the filesystem gets unmounted without closing
GEOM provider etc.
Reviewed by: kib
Approved by: rwatson (mentor)
Tested by: dho
Sponsored by: FreeBSD Foundation
cleanup. Before the GEOM consumer would not have been closed.
- Bump the reference on the character device being mounted while the
associated devfs vnode is locked.
Reviewed by: kib
of devvp becomes VBAD, which UFS incorrectly interprets as snapshot
vnode, which in turns causes panic. Fix it by replacing '!= VCHR'
with '== VREG'.
With this fix in place, you should no longer be able to panic the system
by removing a device with an UFS filesystem mounted from it - assuming
you don't use softupdates.
Reviewed by: kib
Tested by: pho
Approved by: rwatson (mentor)
Sponsored by: FreeBSD Foundation
extended attributes since FreeBSD 5, make the following semantic
changes:
- Don't update the inode modification time (mtime) when extended
attributes (and hence also ACLs) are added, modified, or removed.
- Don't update the inode access tie (atime) when extended attributes
(and hence also ACLs) are queried.
This means that rsync (and related tools) won't improperly think
that the data in the file has changed when only the ACL has changed.
Note that ffs_reallocblks() has not been changed to not update on an
IO_EXT transaction, but currently EAs don't use the cluster write
routines so this shouldn't be a problem. If EAs grow support for
clustering, then VOP_REALLOCBLKS() will need to grow a flag argument
to carry down IO_EXT to UFS.
MFC after: 1 week
PR: ports/125739
Reported by: Alexander Zagrebin <alexz@visp.ru>
Tested by: pluknet <pluknet@gmail.com>,
Greg Byshenk <freebsd@byshenk.net>
Discussed with: kib, kientzle, timur, Alexander Bokovoy <ab@samba.org>
indirect block pages are not removed by the mentioned invocation of
the vnode_pager_setsize().
Put a common code into the helper function ffs_pages_remove().
Reported and tested by: dchagin
Reviewed by: ups
MFC after: 3 weeks
address space where to put vnode pages, and then call UFS_BALLOC(),
to actually allocate new block and map it. When UFS_BALLOC() returns
error, sometimes we forget to revert the vm object size increase,
allowing for the pages that are not backed by the logical disk blocks.
Revert vnode_pager_setsize() back when UFS_BALLOC() failed, for
ffs_truncate() and ffs_write().
PR: 129956
Reviewed by: ups
MFC after: 3 weeks
vnode, from -1 down. When vinvalbuf(vp, V_ALT) is done for the vnode, it
incorrectly does vm_object_page_remove(0, 0), removing all pages from
the underlying vm object, not only the pages that back the extended
attributes data.
Change vinvalbuf() to not remove any pages from the object when
V_NORMAL or V_ALT are specified. Instead, the only in-tree caller
in ffs_inode.c:ffs_truncate() that specifies V_ALT explicitely
removes the corresponding page range. The V_NORMAL caller
does vnode_pager_setsize(vp, 0) immediately after the call to
vinvalbuf(V_NORMAL) already.
Reported by: csjp
Reviewed by: ups
MFC after: 3 weeks
up space. If the buffer cache fills up then the disk systems can
grind to a halt. Better tuning can be figured out later.
Tested by: Tim, others and work
Reviewed by: Kostik Belousov
PR: 128832
- Implement real draining for vfs consumers by not relying on the
mnt_lock and using instead a refcount in order to keep track of lock
requesters.
- Due to the change above, remove the mnt_lock lockmgr because it is now
useless.
- Due to the change above, vfs_busy() is no more linked to a lockmgr.
Change so its KPI by removing the interlock argument and defining 2 new
flags for it: MBF_NOWAIT which basically replaces the LK_NOWAIT of the
old version (which was unlinked from the lockmgr alredy) and
MBF_MNTLSTLOCK which provides the ability to drop the mountlist_mtx
once the mnt interlock is held (ability still desired by most consumers).
- The stub used into vfs_mount_destroy(), that allows to override the
mnt_ref if running for more than 3 seconds, make it totally useless.
Remove it as it was thought to work into older versions.
If a problem of "refcount held never going away" should appear, we will
need to fix properly instead than trust on such hackish solution.
- Fix a bug where returning (with an error) from dounmount() was still
leaving the MNTK_MWAIT flag on even if it the waiters were actually
woken up. Just a place in vfs_mount_destroy() is left because it is
going to recycle the structure in any case, so it doesn't matter.
- Remove the markercnt refcount as it is useless.
This patch modifies VFS ABI and breaks KPI for vfs_busy() so manpages and
__FreeBSD_version will be modified accordingly.
Discussed with: kib
Tested by: pho
to add more V* constants, and the variables changed by this patch were often
being assigned to mode_t variables, which is 16 bit.
Approved by: rwatson (mentor)
and ffs_lock. This cannot catch situations where holdcnt is incremented
not by curthread, but I think it is useful.
Reviewed by: tegge, attilio
Tested by: pho
MFC after: 2 weeks
In particular following functions KPI results modified:
- bufobj_invalbuf()
- bufsync()
and BO_SYNC() "virtual method" of the buffer objects set.
Main consumers of bufobj functions are affected by this change too and,
in particular, functions which changed their KPI are:
- vinvalbuf()
- g_vfs_close()
Due to the KPI breakage, __FreeBSD_version will be bumped in a later
commit.
As a side note, please consider just temporary the 'curthread' argument
passing to VOP_SYNC() (in bufsync()) as it will be axed out ASAP
Reviewed by: kib
Tested by: Giovanni Trematerra <giovanni dot trematerra at gmail dot com>
wait until the current suspension is lifted instead of silently returning
success immediately. The consequences of calling vfs_write() resume when
not owning the suspension are not well-defined at best.
Add the vfs_susp_clean() mount method to be called from
vfs_write_resume(). Set it to process_deferred_inactive() for ffs, and
stop calling it manually.
Add the thread flag TDP_IGNSUSP that allows to bypass the suspension
point in the vn_start_write. It is intended for use by VFS in the
situations where the suspender want to do some i/o requiring calls to
vn_start_write(), and this i/o cannot be done later.
Reviewed by: tegge
In collaboration with: pho
MFC after: 1 month
Show the b_dep value for the buffer in the show buffer command.
Add a comand to dump the dirty/clean buffer list for vnode.
Reviewed by: tegge
Tested and used by: pho
MFC after: 1 month
MNT_RDONLY flag before the VFS_MOUNT() is called. In ufs_inactive()
and ufs_itimes_locked(), UFS verifies whether the fs is read-only by
checking MNT_RDONLY, but this may cause loss of the IN_MODIFIED flag
for inode on the fs being remounted rw->ro.
Introduce UFS_RDONLY() struct ufsmount' method that reports the value
of the fs_ronly. The later is set to 1 only after the remount is
finished.
Reviewed by: tegge
In collaboration with: pho
MFC after: 1 month
inode having number ino. In r170991, the ip was marked IN_MODIFIED, that
is not quite correct.
Mark only the right inode modified by checking inode number.
Reviewed by: tegge
In collaboration with: pho
MFC after: 1 month
insert new vnode into the mount vnode list. Then, for the SU-enabled
mount, ffs_vfree could create freefile dependency. This dependency can
hang around forever since inode is not marked as IN_MODIFIED and
correspondingly inodeblock may be not marked as dirty.
After ffs_vget() fails, retry with FFSV_FORCEINSMQ, mark the inode as
modified, and vput() it immediately. Take care of the dup alloc.
Tested by: pho
Reviewed by: tegge
MFC after: 1 month
dependencies. In particular, it may need this while syncing filesystem
being unmounted. Since during unmount MNTK_NOINSMNTQUE flag is set,
that could sometimes disallow insertion of the vnode into the vnode
mount list, softdep code needs to overwrite the MNTK_NOINSMNTQUE flag.
Create the ffs_vgetf() function that sets the VV_FORCEINSMQ flag for
new vnode and use it consistently from the softdep code instead of
ffs_vget().
Add the retry logic to the softdep_flushfiles() to flush the vnodes
that could be instantiated while flushing softdep dependencies.
Tested by: pho, kris
Reviewed by: tegge
MFC after: 1 month
performed with snapshot option, while the mp->mnt_opt is NULL.
Protect against NULL pointer dereference.
Noted by: Mateusz Guzik <mjguzik gmail com>
MFC after: 3 days
vnode buffers locked at once. In particular, there are indirect buffers
among locked ones. The bdwrite() may start the flushing to keep dirty
buffer list at the bounds. If any buffer on the dirty list requires
translation from logical to physical block number, code may ends up
trying to lock an indirect buffer already locked in ffs_balloc_ufsX.
Prevent the bdflush() activity when several buffers are locked at once
by setting the TDP_INBDFUSH for the problematic code blocks.
Reported and tested by: pho, Josef Buchsteiner at Juniper
In collaboration with: kan
MFC after: 1 month
delete "snapshot" from the persistent mount options list.
This should fix problems with doing a mount -o snapshot of a file system, followed by
an NFS export of the same file system.
PR: 122833
Reported by: Leon Kos <leon.kos lecad fs uni-lj si>,
Jaakko Heinonen <jh saunalahti fi>
MFC after: 1 month
here, because we already do them further up in vfs_donmount() in vfs_mount.c
async -> MNT_ASYNC
force -> MNT_FORCE
multilabel -> MNT_MULTILABEL
noatime -> MNT_NOATIME
noclusterr -> MNT_NOCLUSTERR
noclusterw -> MNT_NOCLUSTERW
MFC after: 1 month
state transitioning flags and of msleep(9) callings.
Use, instead, an algorithm very similar to what sx(9) and rwlock(9)
alredy do and direct accesses to the sleepqueue(9) primitive.
In order to avoid writer starvation a mechanism very similar to what
rwlock(9) uses now is implemented, with the correspective per-thread
shared lockmgrs counter.
This patch also adds 2 new functions to lockmgr KPI: lockmgr_rw() and
lockmgr_args_rw(). These two are like the 2 "normal" versions, but they
both accept a rwlock as interlock. In order to realize this, the general
lockmgr manager function "__lockmgr_args()" has been implemented through
the generic lock layer. It supports all the blocking primitives, but
currently only these 2 mappers live.
The patch drops the support for WITNESS atm, but it will be probabilly
added soon. Also, there is a little race in the draining code which is
also present in the current CVS stock implementation: if some sharers,
once they wakeup, are in the runqueue they can contend the lock with
the exclusive drainer. This is hard to be fixed but the now committed
code mitigate this issue a lot better than the (past) CVS version.
In addition assertive KA_HELD and KA_UNHELD have been made mute
assertions because they are dangerous and they will be nomore supported
soon.
In order to avoid namespace pollution, stack.h is splitted into two
parts: one which includes only the "struct stack" definition (_stack.h)
and one defining the KPI. In this way, newly added _lockmgr.h can
just include _stack.h.
Kernel ABI results heavilly changed by this commit (the now committed
version of "struct lock" is a lot smaller than the previous one) and
KPI results broken by lockmgr_rw() / lockmgr_args_rw() introduction,
so manpages and __FreeBSD_version will be updated accordingly.
Tested by: kris, pho, jeff, danger
Reviewed by: jeff
Sponsored by: Google, Summer of Code program 2007
to protect the v_lock pointer. Removing the interlock acquisition
here allows vn_lock() to proceed without requiring the interlock
at all.
- If the lock mutated while we were sleeping on it the interlock has
been dropped. It is conceivable that the upper layer code was
relying on the interlock and LK_NOWAIT to protect the identity or
state of the vnode while acquiring the lock. In this case return
EBUSY rather than trying the new lock to prevent potential races.
Reviewed by: tegge
Keeping the lockmgr lock valid allows us to switch the v_lock pointer
in snapshot vnodes between the embedded lockmgr lock and snapdata
lock without needing the vnode interlock to protect against races
- Keep unused snapdata structures in a list.
- Add a function to lock the devvp and allocate a snapdata to it or
acquire a new one without races. The old function was safe from
creation races because we set the mount flag when creating snapshots
and thus serializing them. However, it might have been subject to
destroying races.
Reviewed by: tegge
(such as 'atime' vs 'noatime'). The filesystems will always see either
'nofoo' or 'nonofoo', never plain 'foo'. As such, their list of valid
mount options should include 'nofoo' instead of 'foo'. With this fix,
you can do 'mount -u -o atime' on a FFS filesystem that isn't marked as
noatime without getting an error. You can also update a noatime FFS
filesystem mounted via mount(2) (e.g. 6.x /sbin/mount binary) to 'atime'
using nmount(2) (e.g. 7.x /sbin/mount binary).
MFC after: 1 week
Reviewed by: crodig
vnodes belonging to the mountpoint. Also, yield when in the
softdep_process_worklist() even when we are not going to sleep due to
buffer drain.
It is believed that the ULE fixed the problem [1], but the yielding
seems to be needed at least for the 4BSD case.
Discussed: on stable@, with bde
Reviewed by: tegge, jeff [1]
MFC after: 2 weeks
BO_LOCK/UNLOCK/MTX when manipulating the bufobj.
- Create a new lock in the bufobj to lock bufobj fields independently.
This leaves the vnode interlock as an 'identity' lock while the bufobj
is an io lock. The bufobj lock is ordered before the vnode interlock
and also before the mnt ilock.
- Exploit this new lock order to simplify softdep_check_suspend().
- A few sync related functions are marked with a new XXX to note that
we may not properly interlock against a non-zero bv_cnt when
attempting to sync all vnodes on a mountlist. I do not believe this
race is important. If I'm wrong this will make these locations easier
to find.
Reviewed by: kib (earlier diff)
Tested by: kris, pho (earlier diff)
ffs_extread() when setting the IN_ACCESS flag by checking whether the
IN_ACCESS is already set. The possible race there is admissible.
Tested by: pho
Submitted by: jeff
requiring the per-process spinlock to only requiring the process lock.
- Reflect these changes in the proc.h documentation and consumers throughout
the kernel. This is a substantial reduction in locking cost for these
fields and was made possible by recent changes to threading support.
after each SYSINIT() macro invocation. This makes a number of
lightweight C parsers much happier with the FreeBSD kernel
source, including cflow's prcc and lxr.
MFC after: 1 month
Discussed with: imp, rink
callout_* API (e.g. callout_init_mtx(9)). This was one of the numerous
items on the http://wiki.freebsd.org/SMPTODO list.
Reviewed by: imp, obrien, jhb
MFC after: 1 week
It is normally initialized by ffs_statfs() after ffs_mount finished.
The extattr autostart code calls the ufs_lookup(), that uses value above
to iterate over the directory blocks, see bmask initialization in the
ufs_lookup() and ufsdirhash. Having the filesystem with root directory
spanning more then one block would result in reading a random kernel
memory.
PR: kern/120781
Test case provided by: rwatson
MFC after: 1 week
