| Date | Thu, 22 Apr 2010 12:10:31 -0700 | From | Greg KH <> | Subject | [180/197] ext4: flush delalloc blocks when space is low |
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2.6.32-stable review patch. If anyone has any objections, please let us know.
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From: Eric Sandeen <sandeen@redhat.com>
commit c8afb44682fcef6273e8b8eb19fab13ddd05b386 upstream.
Creating many small files in rapid succession on a small filesystem can lead to spurious ENOSPC; on a 104MB filesystem:
for i in `seq 1 22500`; do echo -n > $SCRATCH_MNT/$i echo XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX > $SCRATCH_MNT/$i done
leads to ENOSPC even though after a sync, 40% of the fs is free again.
This is because we reserve worst-case metadata for delalloc writes, and when data is allocated that worst-case reservation is not usually needed.
When freespace is low, kicking off an async writeback will start converting that worst-case space usage into something more realistic, almost always freeing up space to continue.
This resolves the testcase for me, and survives all 4 generic ENOSPC tests in xfstests.
We'll still need a hard synchronous sync to squeeze out the last bit, but this fixes things up to a large degree.
Signed-off-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: maximilian attems <max@stro.at> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/ext4/inode.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
--- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3031,11 +3031,18 @@ static int ext4_nonda_switch(struct supe if (2 * free_blocks < 3 * dirty_blocks || free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) { /* - * free block count is less that 150% of dirty blocks - * or free blocks is less that watermark + * free block count is less than 150% of dirty blocks + * or free blocks is less than watermark */ return 1; } + /* + * Even if we don't switch but are nearing capacity, + * start pushing delalloc when 1/2 of free blocks are dirty. + */ + if (free_blocks < 2 * dirty_blocks) + writeback_inodes_sb_if_idle(sb); + return 0; }
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