[XFS] Catch errors returned from xfs_bmap_last_offset().

xfs_bmap_last_offset() can fail and return an error.
xfs_iomap_write_allocate() fails to detect and propagate the error.

SGI-PV: 980084
SGI-Modid: xfs-linux-melb:xfs-kern:30802a
Signed-off-by: NDavid Chinner <dgc@sgi.com>
Signed-off-by: NNiv Sardi <xaiki@sgi.com>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

fs/xfs/xfs_iomap.c

@@ -802,8 +802,11 @@ xfs_iomap_write_allocate(
 			 */
 			nimaps = 1;
 			end_fsb = XFS_B_TO_FSB(mp, ip->i_size);
-			xfs_bmap_last_offset(NULL, ip, &last_block,
+			error = xfs_bmap_last_offset(NULL, ip, &last_block,
 							XFS_DATA_FORK);
+			if (error)
+				goto trans_cancel;
+
 			last_block = XFS_FILEOFF_MAX(last_block, end_fsb);
 			if ((map_start_fsb + count_fsb) > last_block) {
 				count_fsb = last_block - map_start_fsb;