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| author | Sergei Trofimovich <slyfox@gentoo.org> | 2011-05-20 20:20:30 +0000 |
|---|---|---|
| committer | Chris Mason <chris.mason@oracle.com> | 2011-05-23 13:24:14 -0400 |
| commit | c4f675cd40d955d539180506c09515c90169b15b (patch) | |
| tree | b0960803583fdc03e87255facf3155affa781a9a /fs/btrfs/extent-tree.c | |
| parent | 0f3b708c11914b684d17fed975eed19db902a8de (diff) | |
| download | lwn-c4f675cd40d955d539180506c09515c90169b15b.tar.gz lwn-c4f675cd40d955d539180506c09515c90169b15b.zip | |
btrfs: don't spin in shrink_delalloc if there is nothing to free
Observed as a large delay when --mixed filesystem is filled up.
Test example:
1. create tiny --mixed FS:
$ dd if=/dev/zero of=2G.img seek=$((2048 * 1024 * 1024 - 1)) count=1 bs=1
$ mkfs.btrfs --mixed 2G.img
$ mount -oloop 2G.img /mnt/ut/
2. Try to fill it up:
$ dd if=/dev/urandom of=10M.file bs=10240 count=1024
$ seq 1 256 | while read file_no; do echo $file_no; time cp 10M.file ${file_no}.copy; done
Up to '200.copy' it goes fast, but when disk fills-up each -ENOSPC
message takes 3 seconds to pop-up _every_ ENOSPC (and in usermode linux
it's even more: 30-60 seconds!). (Maybe, time depends on kernel's timer resolution).
No IO, no CPU load, just rescheduling. Some debugging revealed busy spinning
in shrink_delalloc.
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Reviewed-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/extent-tree.c')
| -rw-r--r-- | fs/btrfs/extent-tree.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 9ee6bd55e16c..9f5fdd37451d 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3425,6 +3425,10 @@ static int shrink_delalloc(struct btrfs_trans_handle *trans, if (reserved == 0) return 0; + /* nothing to shrink - nothing to reclaim */ + if (root->fs_info->delalloc_bytes == 0) + return 0; + max_reclaim = min(reserved, to_reclaim); while (loops < 1024) { |