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authorSergei Trofimovich <slyfox@gentoo.org>2011-05-20 20:20:30 +0000
committerChris Mason <chris.mason@oracle.com>2011-05-23 13:24:14 -0400
commitc4f675cd40d955d539180506c09515c90169b15b (patch)
treeb0960803583fdc03e87255facf3155affa781a9a /fs/btrfs
parent0f3b708c11914b684d17fed975eed19db902a8de (diff)
downloadop-kernel-dev-c4f675cd40d955d539180506c09515c90169b15b.zip
op-kernel-dev-c4f675cd40d955d539180506c09515c90169b15b.tar.gz
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')
-rw-r--r--fs/btrfs/extent-tree.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 9ee6bd5..9f5fdd3 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) {
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