GFS2: Stop looking for free blocks at end of rgrp

This patch adds a return code check after calling function
gfs2_rbm_from_block while determining the free extent size.
That way, when the end of an rgrp is reached, it won't try
to process unaligned blocks after the end.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/rgrp.c

@@ -350,10 +350,14 @@ static u32 gfs2_free_extlen(const struct gfs2_rbm *rrbm, u32 len)
 		BUG_ON(len < chunk_size);
 		len -= chunk_size;
 		block = gfs2_rbm_to_block(&rbm);
-		gfs2_rbm_from_block(&rbm, block + chunk_size);
-		n_unaligned = 3;
-		if (ptr)
+		if (gfs2_rbm_from_block(&rbm, block + chunk_size)) {
+			n_unaligned = 0;
 			break;
+		}
+		if (ptr) {
+			n_unaligned = 3;
+			break;
+		}
 		n_unaligned = len & 3;
 	}