xfs: dont ignore error code from xfs_bmbt_update

Fix a case in xfs_bmap_add_extent_unwritten_real where we aren't
passing the returned error on.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_bmap.c

@@ -1217,10 +1217,11 @@ xfs_bmap_add_extent_unwritten_real(
 				goto done;
 			if ((error = xfs_btree_decrement(cur, 0, &i)))
 				goto done;
-			if (xfs_bmbt_update(cur, LEFT.br_startoff,
+			error = xfs_bmbt_update(cur, LEFT.br_startoff,
 				LEFT.br_startblock,
 				LEFT.br_blockcount + new->br_blockcount,
-				LEFT.br_state))
+				LEFT.br_state);
+			if (error)
 				goto done;
 		}
 		break;