Commit 1b4998dc authored Oct 03, 2017 by Christoph Hellwig Committed by Greg Kroah-Hartman Oct 27, 2017

xfs: handle racy AIO in xfs_reflink_end_cow



commit e12199f85d0ad1b04ce6c425ad93cd847fe930bb upstream.

If we got two AIO writes into a COW area the second one might not have any
COW extents left to convert.  Handle that case gracefully instead of
triggering an assert or accessing beyond the bounds of the extent list.

Signed-off-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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 002295a6

fs/xfs/xfs_reflink.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -767,7 +767,13 @@ xfs_reflink_end_cow(

		/* If there is a hole at end_fsb - 1 go to the previous extent */
		if (eof \|\| got.br_startoff > end_fsb) {
		ASSERT(idx > 0);
		/*
		* 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 case we are done.
		*/
		if (idx <= 0)
		goto out_cancel;
		xfs_bmbt_get_all(xfs_iext_get_ext(ifp, --idx), &got);
		}

		@@ -841,6 +847,7 @@ xfs_reflink_end_cow(

		out_defer:
		xfs_defer_cancel(&dfops);
		out_cancel:
		xfs_trans_cancel(tp);
		xfs_iunlock(ip, XFS_ILOCK_EXCL);
		out: