linux-toradex.git/fs/sync.c, branch tegra-10.9.7

fs/buffer.c: clean up EXPORT* macros

2009-09-23T14:39:29+00:00

According to Documentation/CodingStyle the EXPORT* macro should follow
immediately after the closing function brace line.

Also, mark_buffer_async_write_endio() and do_thaw_all() are not used
elsewhere so they should be marked as static.

In addition, file_fsync() is actually in fs/sync.c so move the EXPORT* to
that file.

Signed-off-by: H Hartley Sweeten 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fs: Assign bdi in super_block

2009-09-16T13:18:51+00:00

We do this automatically in get_sb_bdev() from the set_bdev_super()
callback. Filesystems that have their own private backing_dev_info
must assign that in ->fill_super().

Note that ->s_bdi assignment is required for proper writeback!

Acked-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

fsync: wait for data writeout completion before calling ->fsync

2009-09-14T15:08:17+00:00

Currenly vfs_fsync(_range) first calls filemap_fdatawrite to write out
the data, the calls into ->fsync to write out the metadata and then finally
calls filemap_fdatawait to wait for the data I/O to complete.  What sounds
like a clever micro-optimization actually is nast trap for many filesystems.

For many modern filesystems i_size or other inode information is only
updated on I/O completion and we need to wait for I/O to finish before
we can write out the metadata.  For old fashionen filesystems that
instanciate blocks during the actual write and also update the metadata
at that point it opens up a large window were we could expose uninitialized
blocks after a crash.  While a few filesystems that need it already wait
for the I/O to finish inside their ->fsync methods it is rather suboptimal
as it is done under the i_mutex and also always for the whole file instead
of just a part as we could do for O_SYNC handling.

Here is a small audit of all fsync instances in the tree:

 - spufs_mfc_fsync:
 - ps3flash_fsync:
 - vol_cdev_fsync:
 - printer_fsync:
 - fb_deferred_io_fsync:
 - bad_file_fsync:
 - simple_sync_file:

	don't care - filesystems/drivers do't use the page cache or are
	purely in-memory.

 - simple_fsync:
 - file_fsync:
 - affs_file_fsync:
 - fat_file_fsync:
 - jfs_fsync:
 - ubifs_fsync:
 - reiserfs_dir_fsync:
 - reiserfs_sync_file:

	never touch pagecache themselves.  We need to wait before if we do
	not want to expose stale data after an allocation.

 - afs_fsync:
 - fuse_fsync_common:

	do the waiting writeback itself in awkward ways, would benefit from
	proper semantics

 - block_fsync:

	Does a filemap_write_and_wait on the block device inode.  Because we
	now have f_mapping that is the same inode we call it on in vfs_fsync.
	So just removing it and letting the VFS do the work in one go would
	be an improvement.

 - btrfs_sync_file:
 - cifs_fsync:
 - xfs_file_fsync:

	need the wait first and currently do it themselves. would benefit from
	doing it outside i_mutex.

 - coda_fsync:
 - ecryptfs_fsync:
 - exofs_file_fsync:
 - shm_fsync:

	only passes the fsync through to the lower layer

 - ext3_sync_file:

	doesn't seem to care, comments are confusing.

 - ext4_sync_file:

	would need the wait to work correctly for delalloc mode with late
	i_size updates.  Otherwise the ext3 comment applies.

	currently implemens it's own writeback and wait in an odd way,
	could benefit from doing it properly.

 - gfs2_fsync:

	not needed for journaled data mode, but probably harmless there.
	Currently writes back data asynchronously itself.  Needs some
	major audit.

 - hostfs_fsync:

	just calls fsync/datasync on the host FD.  Without the wait before
	data might not even be inflight yet if we're unlucky.

 - hpfs_file_fsync:
 - ncp_fsync:

	no-ops.  Dangerous before and after.

 - jffs2_fsync:

	just calls jffs2_flush_wbuf_gc, not sure how this relates to data.

 - nfs_fsync_dir:

	just increments stats, claims all directory operations are synchronous

 - nfs_file_fsync:

	only writes out data???  Looks very odd.

 - nilfs_sync_file:

	looks like it expects all data done, but not sure from the code

 - ntfs_dir_fsync:
 - ntfs_file_fsync:

	appear to do their own data writeback.  Very convoluted code.

 - ocfs2_sync_file:

	does it's own data writeback, but no wait.  probably needs the wait.

 - smb_fsync:

	according to a comment expects all pages written already, probably needs
	the wait before.

This patch only changes vfs_fsync_range, removal of the wait in the methods
that have it is left to the filesystem maintainers.  Note that most
filesystems really do need an audit for their fsync methods given the
gems found in this very brief audit.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jan Kara

vfs: Introduce new helpers for syncing after writing to O_SYNC file or IS_SYNC inode

2009-09-14T15:08:15+00:00

Introduce new function for generic inode syncing (vfs_fsync_range) and use
it from fsync() path. Introduce also new helper for syncing after a sync
write (generic_write_sync) using the generic function.

Use these new helpers for syncing from generic VFS functions. This makes
O_SYNC writes to block devices acquire i_mutex for syncing. If we really
care about this, we can make block_fsync() drop the i_mutex and reacquire
it before it returns.

CC: Evgeniy Polyakov 
CC: ocfs2-devel@oss.oracle.com
CC: Joel Becker 
CC: Felix Blyakher 
CC: xfs@oss.sgi.com
CC: Anton Altaparmakov 
CC: linux-ntfs-dev@lists.sourceforge.net
CC: OGAWA Hirofumi 
CC: linux-ext4@vger.kernel.org
CC: tytso@mit.edu
Acked-by: Christoph Hellwig 
Signed-off-by: Jan Kara

writeback: switch to per-bdi threads for flushing data

2009-09-11T07:20:25+00:00

This gets rid of pdflush for bdi writeout and kupdated style cleaning.
pdflush writeout suffers from lack of locality and also requires more
threads to handle the same workload, since it has to work in a
non-blocking fashion against each queue. This also introduces lumpy
behaviour and potential request starvation, since pdflush can be starved
for queue access if others are accessing it. A sample ffsb workload that
does random writes to files is about 8% faster here on a simple SATA drive
during the benchmark phase. File layout also seems a LOT more smooth in
vmstat:

 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 0  1      0 608848   2652 375372    0    0     0 71024  604    24  1 10 48 42
 0  1      0 549644   2712 433736    0    0     0 60692  505    27  1  8 48 44
 1  0      0 476928   2784 505192    0    0     4 29540  553    24  0  9 53 37
 0  1      0 457972   2808 524008    0    0     0 54876  331    16  0  4 38 58
 0  1      0 366128   2928 614284    0    0     4 92168  710    58  0 13 53 34
 0  1      0 295092   3000 684140    0    0     0 62924  572    23  0  9 53 37
 0  1      0 236592   3064 741704    0    0     4 58256  523    17  0  8 48 44
 0  1      0 165608   3132 811464    0    0     0 57460  560    21  0  8 54 38
 0  1      0 102952   3200 873164    0    0     4 74748  540    29  1 10 48 41
 0  1      0  48604   3252 926472    0    0     0 53248  469    29  0  7 47 45

where vanilla tends to fluctuate a lot in the creation phase:

 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 1  1      0 678716   5792 303380    0    0     0 74064  565    50  1 11 52 36
 1  0      0 662488   5864 319396    0    0     4   352  302   329  0  2 47 51
 0  1      0 599312   5924 381468    0    0     0 78164  516    55  0  9 51 40
 0  1      0 519952   6008 459516    0    0     4 78156  622    56  1 11 52 37
 1  1      0 436640   6092 541632    0    0     0 82244  622    54  0 11 48 41
 0  1      0 436640   6092 541660    0    0     0     8  152    39  0  0 51 49
 0  1      0 332224   6200 644252    0    0     4 102800  728    46  1 13 49 36
 1  0      0 274492   6260 701056    0    0     4 12328  459    49  0  7 50 43
 0  1      0 211220   6324 763356    0    0     0 106940  515    37  1 10 51 39
 1  0      0 160412   6376 813468    0    0     0  8224  415    43  0  6 49 45
 1  1      0  85980   6452 886556    0    0     4 113516  575    39  1 11 54 34
 0  2      0  85968   6452 886620    0    0     0  1640  158   211  0  0 46 54

A 10 disk test with btrfs performs 26% faster with per-bdi flushing. A
SSD based writeback test on XFS performs over 20% better as well, with
the throughput being very stable around 1GB/sec, where pdflush only
manages 750MB/sec and fluctuates wildly while doing so. Random buffered
writes to many files behave a lot better as well, as does random mmap'ed
writes.

A separate thread is added to sync the super blocks. In the long term,
adding sync_supers_bdi() functionality could get rid of this thread again.

Signed-off-by: Jens Axboe

writeback: get rid of generic_sync_sb_inodes() export

2009-09-11T07:20:25+00:00

This adds two new exported functions:

- writeback_inodes_sb(), which only attempts to writeback dirty inodes on
  this super_block, for WB_SYNC_NONE writeout.
- sync_inodes_sb(), which writes out all dirty inodes on this super_block
  and also waits for the IO to complete.

Acked-by: Jan Kara 
Signed-off-by: Jens Axboe

sys_sync(): fix 16% performance regression in ffsb create_4k test

2009-07-06T20:57:03+00:00

I run many ffsb test cases on JBODs (typically 13/12 disks).  Comparing
with kernel 2.6.30, 2.6.31-rc1 has about 16% regression with
ffsb_create_4k.  The sub test case creates files continuously for 10
minitues and every file is 1MB.

Bisect located below patch.

5cee5815d1564bbbd505fea86f4550f1efdb5cd0 is first bad commit
commit 5cee5815d1564bbbd505fea86f4550f1efdb5cd0
Author: Jan Kara 
Date:   Mon Apr 27 16:43:51 2009 +0200

    vfs: Make sys_sync() use fsync_super() (version 4)

    It is unnecessarily fragile to have two places (fsync_super() and do_sync())
    doing data integrity sync of the filesystem. Alter __fsync_super() to
    accommodate needs of both callers and use it. So after this patch
    __fsync_super() is the only place where we gather all the calls needed to
    properly send all data on a filesystem to disk.

As a matter of fact, ffsb calls sys_sync in the end to make sure all data
is flushed to disks and the flushing is counted into the result.  vmstat
shows ffsb is blocked when syncing for a long time.  With 2.6.30, ffsb is
blocked for a short time.

I checked the patch and did experiments to recover the original methods.
Eventually, the root cause is the patch deletes the calling to
wakeup_pdflush when syncing, so only ffsb is blocked on disk I/O.
wakeup_pdflush could ask pdflush to write back pages with ffsb at the
same time.

[akpm@linux-foundation.org: restore comment too]
Signed-off-by: Zhang Yanmin 
Cc: Jan Kara 
Cc: Al Viro 
Acked-by: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

remove the call to ->write_super in __sync_filesystem

2009-06-12T01:36:17+00:00

Now that all filesystems provide ->sync_fs methods we can change
__sync_filesystem to only call ->sync_fs.

This gives us a clear separation between periodic writeouts which
are driven by ->write_super and data integrity syncs that go
through ->sync_fs. (modulo file_fsync which is also going away)

Signed-off-by: Christoph Hellwig 
Signed-off-by: Al Viro

->write_super lock_super pushdown

2009-06-12T01:36:09+00:00

Push down lock_super into ->write_super instances and remove it from the
caller.

Following filesystem don't need ->s_lock in ->write_super and are skipped:

 * bfs, nilfs2 - no other uses of s_lock and have internal locks in
	->write_super
 * ext2 - uses BKL in ext2_write_super and has internal calls without s_lock
 * reiserfs - no other uses of s_lock as has reiserfs_write_lock (BKL) in
 	->write_super
 * xfs - no other uses of s_lock and uses internal lock (buffer lock on
	superblock buffer) to serialize ->write_super.  Also xfs_fs_write_super
	is superflous and will go away in the next merge window

Signed-off-by: Christoph Hellwig 
Signed-off-by: Al Viro

enforce ->sync_fs is only called for rw superblock

2009-06-12T01:36:06+00:00

Make sure a superblock really is writeable by checking MS_RDONLY
under s_umount.  sync_filesystems needed some re-arragement for
that, but all but one sync_filesystem caller had the correct locking
already so that we could add that check there.  cachefiles grew
s_umount locking.

I've also added a WARN_ON to sync_filesystem to assert this for
future callers.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Al Viro