Commit 3dd09d5a authored Apr 03, 2017 by Calvin Owens Committed by Darrick J. Wong Apr 03, 2017

xfs: Honor FALLOC_FL_KEEP_SIZE when punching ends of files



When punching past EOF on XFS, fallocate(mode=PUNCH_HOLE|KEEP_SIZE) will
round the file size up to the nearest multiple of PAGE_SIZE:

  calvinow@vm-disks/generic-xfs-1 ~$ dd if=/dev/urandom of=test bs=2048 count=1
  calvinow@vm-disks/generic-xfs-1 ~$ stat test
    Size: 2048            Blocks: 8          IO Block: 4096   regular file
  calvinow@vm-disks/generic-xfs-1 ~$ fallocate -n -l 2048 -o 2048 -p test
  calvinow@vm-disks/generic-xfs-1 ~$ stat test
    Size: 4096            Blocks: 8          IO Block: 4096   regular file

Commit 3c2bdc91 ("xfs: kill xfs_zero_remaining_bytes") replaced
xfs_zero_remaining_bytes() with calls to iomap helpers. The new helpers
don't enforce that [pos,offset) lies strictly on [0,i_size) when being
called from xfs_free_file_space(), so by "leaking" these ranges into
xfs_zero_range() we get this buggy behavior.

Fix this by reintroducing the checks xfs_zero_remaining_bytes() did
against i_size at the bottom of xfs_free_file_space().

Reported-by: Aaron Gao <gzh@fb.com>
Fixes: 3c2bdc91 ("xfs: kill xfs_zero_remaining_bytes")
Cc: Christoph Hellwig <hch@lst.de>
Cc: Brian Foster <bfoster@redhat.com>
Cc: <stable@vger.kernel.org> # 4.8+
Signed-off-by: Calvin Owens <calvinowens@fb.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 78420281

fs/xfs/xfs_bmap_util.c

+9 −1

Original line number	Original line	Diff line number	Diff line
	@@ -1311,8 +1311,16 @@ xfs_free_file_space(
	/*		/*
	* Now that we've unmap all full blocks we'll have to zero out any		* Now that we've unmap all full blocks we'll have to zero out any
	* partial block at the beginning and/or end. xfs_zero_range is		* partial block at the beginning and/or end. xfs_zero_range is
	* smart enough to skip any holes, including those we just created.		* smart enough to skip any holes, including those we just created,
			* but we must take care not to zero beyond EOF and enlarge i_size.
	*/		*/

			if (offset >= XFS_ISIZE(ip))
			return 0;

			if (offset + len > XFS_ISIZE(ip))
			len = XFS_ISIZE(ip) - offset;

	return xfs_zero_range(ip, offset, len, NULL);		return xfs_zero_range(ip, offset, len, NULL);
	}		}

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