xfs: fix extent busy updating

In xfs_extent_busy_update_extent() case 6 and 7, whenever bno is modified on
extent busy, the relavent length has to be modified accordingly.
Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/xfs_extent_busy.c

@@ -236,6 +236,7 @@ xfs_extent_busy_update_extent(
 		 *
 		 */
 		busyp->bno = fend;
+		busyp->length = bend - fend;
 	} else if (bbno < fbno) {
 		/*
 		 * Case 8: