The buffered write failure handling code in
xfs_file_iomap_end_delalloc() has a couple minor problems. First, if
written == 0, start_fsb is not rounded down and it fails to kill off a
delalloc block if the start offset is block unaligned. This results in a
lingering delalloc block and broken delalloc block accounting detected
at unmount time. Fix this by rounding down start_fsb in the unlikely
event that written == 0.
Second, it is possible for a failed overwrite of a delalloc extent to
leave dirty pagecache around over a hole in the file. This is because is
possible to hit ->iomap_end() on write failure before the iomap code has
attempted to allocate pagecache, and thus has no need to clean it up. If
the targeted delalloc extent was successfully written by a previous
write, however, then it does still have dirty pages when ->iomap_end()
punches out the underlying blocks. This ultimately results in writeback
over a hole. To fix this problem, unconditionally punch out the
pagecache from XFS before the associated delalloc range.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
v2:
- Used if/else logic and added a comment.
fs/xfs/xfs_iomap.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index e0bc290..4009e7c 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1078,7 +1078,15 @@ xfs_file_iomap_end_delalloc(
xfs_fileoff_t end_fsb;
int error = 0;
- start_fsb = XFS_B_TO_FSB(mp, offset + written);
+ /*
+ * start_fsb refers to the first unused block after a short write. If
+ * nothing was written, round offset down to point at the first block in
+ * the range.
+ */
+ if (unlikely(!written))
+ start_fsb = XFS_B_TO_FSBT(mp, offset);
+ else
+ start_fsb = XFS_B_TO_FSB(mp, offset + written);
end_fsb = XFS_B_TO_FSB(mp, offset + length);
/*
@@ -1090,6 +1098,9 @@ xfs_file_iomap_end_delalloc(
* blocks in the range, they are ours.
*/
if (start_fsb < end_fsb) {
+ truncate_pagecache_range(VFS_I(ip), XFS_FSB_TO_B(mp, start_fsb),
+ XFS_FSB_TO_B(mp, end_fsb) - 1);
+
xfs_ilock(ip, XFS_ILOCK_EXCL);
error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
end_fsb - start_fsb);
--
2.7.4
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