When running the 083th case of xfstests on the filesystem with
"compress-force=lzo", the following WARNINGs were triggered.
WARNING: at fs/btrfs/inode.c:7908
WARNING: at fs/btrfs/inode.c:7909
WARNING: at fs/btrfs/inode.c:7911
WARNING: at fs/btrfs/extent-tree.c:4510
WARNING: at fs/btrfs/extent-tree.c:4511
This problem was introduced by the patch "Btrfs: fix deadlock due
to unsubmitted". In this patch, there are two bugs which caused
the above problem.
The 1st one is a off-by-one bug, if the DIO write return 0, it is
also a short write, we need release the reserved space for it. But
we didn't do it in that patch. Fix it by change "ret > 0" to
"ret >= 0".
The 2nd one is ->outstanding_extents was increased twice when
a short write happened. As we know, ->outstanding_extents is
a counter to keep track of the number of extent items we may
use duo to delalloc, when we reserve the free space for a
delalloc write, we assume that the write will introduce just
one extent item, so we increase ->outstanding_extents by 1 at
that time. And then we will increase it every time we split the
write, it is done at the beginning of btrfs_get_blocks_direct().
So when a short write happens, we needn't increase
->outstanding_extents again. But this patch done.
In order to fix the 2nd problem, I re-write the logic for
->outstanding_extents operation. We don't increase it at the
beginning of btrfs_get_blocks_direct(), instead, we just
increase it when the split actually happens.
Reported-by: Mitch Harder <mitch.harder@xxxxxxxxxxxxxxxx>
Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
---
fs/btrfs/inode.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b009fb5..9a1cc04 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6067,12 +6067,9 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
int unlock_bits = EXTENT_LOCKED;
int ret = 0;
- if (create) {
- spin_lock(&BTRFS_I(inode)->lock);
- BTRFS_I(inode)->outstanding_extents++;
- spin_unlock(&BTRFS_I(inode)->lock);
+ if (create)
unlock_bits |= EXTENT_DELALLOC | EXTENT_DIRTY;
- } else
+ else
len = min_t(u64, len, root->sectorsize);
lockstart = start;
@@ -6214,6 +6211,10 @@ unlock:
if (start + len > i_size_read(inode))
i_size_write(inode, start + len);
+ spin_lock(&BTRFS_I(inode)->lock);
+ BTRFS_I(inode)->outstanding_extents++;
+ spin_unlock(&BTRFS_I(inode)->lock);
+
ret = set_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
lockstart + len - 1, EXTENT_DELALLOC, NULL,
&cached_state, GFP_NOFS);
@@ -6716,14 +6717,11 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
if (rw & WRITE) {
if (ret < 0 && ret != -EIOCBQUEUED)
btrfs_delalloc_release_space(inode, count);
- else if (ret > 0 && (size_t)ret < count) {
- spin_lock(&BTRFS_I(inode)->lock);
- BTRFS_I(inode)->outstanding_extents++;
- spin_unlock(&BTRFS_I(inode)->lock);
+ else if (ret >= 0 && (size_t)ret < count)
btrfs_delalloc_release_space(inode,
count - (size_t)ret);
- }
- btrfs_delalloc_release_metadata(inode, 0);
+ else
+ btrfs_delalloc_release_metadata(inode, 0);
}
out:
if (wakeup)
--
1.7.11.7
--
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