Commit fa7f138a authored Feb 16, 2017 by Brian Foster Committed by Darrick J. Wong Feb 16, 2017

xfs: clear delalloc and cache on buffered write failure

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@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

parent 4560e78f

fs/xfs/xfs_iomap.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -1078,6 +1078,14 @@ xfs_file_iomap_end_delalloc(
		xfs_fileoff_t end_fsb;
		int error = 0;

		/*
		* 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);

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