[PATCH v2 0/3] btrfs: don't spin in shrink_delalloc if there is nothing to free

[PATCH v2 0/3] btrfs: don't spin in shrink_delalloc if there is nothing to free

[Sergei Trofimovich]

The really interesting commit is
    btrfs: don't spin in shrink_delalloc if there is nothing to free
which fixes hogs on ENOSPC for me.


The rest of patches are cleanup.

Change since v2:
- Rebased against 2.6.39

Change since v1:
- Added Josef's Reviewed-by
- Fixed my MTA and patch numbering

Thanks!

P.S.:
It's also interesting to note, that 'shrink_delalloc' tries
to mess with 'bytes_reserved' (which are metadata reservation
right?)

The more I look at 'bytes_reserved' management paths the more I
think 'shrink_delalloc' should not touch them.

[[PATCH v3] 1/3] btrfs: don't spin in shrink_delalloc if there is nothing to free

[Sergei Trofimovich]

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>
---
 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 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) {
-- 
1.7.3.4

[[PATCH v3] 2/3] btrfs: typo: 'btrfS' -> 'btrfs'

[Sergei Trofimovich]

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
---
 fs/btrfs/dir-item.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index c62f02f..dec9348 100644
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -452,7 +452,7 @@ int verify_dir_item(struct btrfs_root *root,
 		namelen = XATTR_NAME_MAX;
 
 	if (btrfs_dir_name_len(leaf, dir_item) > namelen) {
-		printk(KERN_CRIT "btrfS: invalid dir item name len: %u\n",
+		printk(KERN_CRIT "btrfs: invalid dir item name len: %u\n",
 		       (unsigned)btrfs_dir_data_len(leaf, dir_item));
 		return 1;
 	}
-- 
1.7.3.4

[[PATCH v3] 3/3] btrfs: fix typo 'testeing' -> 'testing'

[Sergei Trofimovich]

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
---
 fs/btrfs/inode.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 7cd8ab0..72650ce 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1310,7 +1310,7 @@ static int btrfs_set_bit_hook(struct inode *inode,
 
 	/*
 	 * set_bit and clear bit hooks normally require _irqsave/restore
-	 * but in this case, we are only testeing for the DELALLOC
+	 * but in this case, we are only testing for the DELALLOC
 	 * bit, which is only set or cleared with irqs on
 	 */
 	if (!(state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
@@ -1344,7 +1344,7 @@ static int btrfs_clear_bit_hook(struct inode *inode,
 {
 	/*
 	 * set_bit and clear bit hooks normally require _irqsave/restore
-	 * but in this case, we are only testeing for the DELALLOC
+	 * but in this case, we are only testing for the DELALLOC
 	 * bit, which is only set or cleared with irqs on
 	 */
 	if ((state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
-- 
1.7.3.4