When a file is first being written, the dynamic block reallocation
(implemented by ext2_reallocblks) relocates the file's blocks
so as to cluster them together into a contiguous set of blocks on
the disk.
When the cluster crosses the boundary into the first indirect block,
the first indirect block is initially allocated in a position
immediately following the last direct block. Block reallocation
would usually destroy locality by moving the indirect block out of
the way to keep the data blocks contiguous.
The issue was diagnosed long ago by Bruce Evans on ffs and surfaced
on ext2fs when block reallocaton was ported. This is only a partial
solution based on the similarities with FFS. We still require more
review of the allocation details that vary in ext2fs.
Reported by: bde
MFC after: 1 week
When using big inodes there is sufficient space in ext3 to
keep extra resolution and birthtime (creation) timestamps.
The appropriate fields in the on-disk inode have been approved
for a long time but support for this in ext3 has not been
widely distributed.
In preparation for ext4 most linux distributions have enabled
by default such bigger inodes and some people use nanosecond
timestamps in ext3. We now support those when the inode is big
enough and while we do recognize the EXT4F_ROCOMPAT_EXTRA_ISIZE,
we maintain the extra timestamps even when they are not used.
An additional note by Bruce Evans:
We blindly accept unrepresentable tv_nsec in VOP_SETATTR(), but
all file systems have always done that. When POSIX gets around
to specifying the behaviour, it will probably require certain
rounding to the fs's resolution and not rejecting the request.
This unfortunately means that syscalls that set times can't
really tell if they succeeded without reading back the times
using stat() or similar and checking that they were set close
enough.
Reviewed by: bde
Approved by: jhb (mentor)
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.
Fix a comment from the previous commit.
Use M_ZERO instead of bzero() in ext2_vfsops.c
Add include guards from PR.
PR: 162564
Approved by: jhb (mentor)
MFC after: 2 weeks
The feature has been standard for a while in UFS as a means to reduce
fragmentation, therefore maintaining consistent performance with
filesystem aging. This is also very similar to what ext4 calls
"delayed allocation".
In his 2010 GSoC, Zheng Liu ported and benchmarked the missing
FANCY_REALLOC code to find more consistent performance improvements than
with the preallocation approach.
PR: 159233
Author: Zheng Liu <gnehzuil AT SPAMFREE gmail DOT com>
Sponsored by: Google Inc.
Approved by: jhb (mentor)
MFC after: 2 weeks
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.
free i-nodes or blocks to handle a race where another thread might have
allocated the last i-node or block while we were waiting for the buffer.
Tested by: dougb
so that future allocations start with most recently allocated block
rather than the beginning of the filesystem.
- Fix ext2_alloccg() to properly scan for 8 block chunks that are not
aligned on 8-bit boundaries. Previously this was causing new blocks
to be allocated in a highly fragmented fashion (block 0 of a file at
lbn N, block 1 at lbn N + 8, block 2 at lbn N + 16, etc.).
- Cosmetic tweaks to the currently-disabled fancy realloc sysctls.
PR: kern/153584
Discussed with: bde
Tested by: Pedro F. Giffuni giffunip at yahoo, Zheng Liu (lz)
of Code 2009:
- BSDL block and inode allocation policies for ext2fs. This involves the use
FFS1 style block and inode allocation for ext2fs. Preallocation was removed
since it was GPL'd.
- Make ext2fs MPSAFE by introducing locks to per-mount datastructures.
- Fixes for kern/122047 PR.
- Various small bugfixes.
- Move out of gnu/ directory.
Sponsored by: Google Inc.
Submitted by: Aditya Sarawgi <sarawgi.aditya AT SPAMFREE gmail DOT com>
