Commit 5f1d5bbf authored Jan 22, 2021 by Chandan Babu R Committed by Darrick J. Wong Jan 22, 2021

xfs: Check for extent overflow when moving extent from cow to data fork



Moving an extent to data fork can cause a sub-interval of an existing
extent to be unmapped. This will increase extent count by 1. Mapping in
the new extent can increase the extent count by 1 again i.e.
 | Old extent | New extent | Old extent |
Hence number of extents increases by 2.

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

parent c442f308

fs/xfs/libxfs/xfs_inode_fork.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -79,6 +79,15 @@ struct xfs_ifork {
		#define XFS_IEXT_WRITE_UNWRITTEN_CNT (2)


		/*
		* Moving an extent to data fork can cause a sub-interval of an existing extent
		* to be unmapped. This will increase extent count by 1. Mapping in the new
		* extent can increase the extent count by 1 again i.e.
		* \| Old extent \| New extent \| Old extent \|
		* Hence number of extents increases by 2.
		*/
		#define XFS_IEXT_REFLINK_END_COW_CNT (2)

		/*
		* Fork handling.
		*/

fs/xfs/xfs_reflink.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -628,6 +628,11 @@ xfs_reflink_end_cow_extent(
		xfs_ilock(ip, XFS_ILOCK_EXCL);
		xfs_trans_ijoin(tp, ip, 0);

		error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
		XFS_IEXT_REFLINK_END_COW_CNT);
		if (error)
		goto out_cancel;

		/*
		* In case of racing, overlapping AIO writes no COW extents might be
		* left by the time I/O completes for the loser of the race. In that