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authorEric Sandeen <sandeen@redhat.com>2009-12-23 07:58:12 -0500
committerTheodore Ts'o <tytso@mit.edu>2009-12-23 07:58:12 -0500
commitc8afb44682fcef6273e8b8eb19fab13ddd05b386 (patch)
tree44c170427e54b611d7f02a31bbd5733cc9cf1dd0
parent17bd55d037a02b04d9119511cfd1a4b985d20f63 (diff)
ext4: flush delalloc blocks when space is low
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>
-rw-r--r--fs/ext4/inode.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ab807963a614..282621f18c10 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2993,11 +2993,18 @@ static int ext4_nonda_switch(struct super_block *sb)
2993 if (2 * free_blocks < 3 * dirty_blocks || 2993 if (2 * free_blocks < 3 * dirty_blocks ||
2994 free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) { 2994 free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) {
2995 /* 2995 /*
2996 * free block count is less that 150% of dirty blocks 2996 * free block count is less than 150% of dirty blocks
2997 * or free blocks is less that watermark 2997 * or free blocks is less than watermark
2998 */ 2998 */
2999 return 1; 2999 return 1;
3000 } 3000 }
3001 /*
3002 * Even if we don't switch but are nearing capacity,
3003 * start pushing delalloc when 1/2 of free blocks are dirty.
3004 */
3005 if (free_blocks < 2 * dirty_blocks)
3006 writeback_inodes_sb_if_idle(sb);
3007
3001 return 0; 3008 return 0;
3002} 3009}
3003 3010