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Date: Fri, 24 Feb 2017 09:38:16 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Brian Foster <bfoster@...hat.com>, Christoph Hellwig <hch@....de>, "Darrick J. Wong" <darrick.wong@...cle.com> Subject: [PATCH 4.9 32/32] xfs: clear delalloc and cache on buffered write failure 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Brian Foster <bfoster@...hat.com> commit fa7f138ac4c70dc00519c124cf7cd4862a0a5b0e upstream. 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@...hat.com> Reviewed-by: Christoph Hellwig <hch@....de> Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- fs/xfs/xfs_iomap.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -1068,7 +1068,15 @@ 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); /* @@ -1080,6 +1088,9 @@ 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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