[GFS2] possible null pointer dereference fixup

gfs2_alloc_get may fail so we have to check it to prevent
NULL pointer dereference.

Signed-off-by: Cyrill Gorcunov <gorcunov@gamil.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index c1ee635..f7093aa 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -900,6 +900,8 @@
 	int error;
 
 	al = gfs2_alloc_get(ip);
+	if (!al)
+		return -ENOMEM;
 
 	error = gfs2_quota_lock(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
 	if (error)
@@ -1081,7 +1083,8 @@
 		lblock = (size - 1) >> sdp->sd_sb.sb_bsize_shift;
 
 	find_metapath(sdp, lblock, &mp, ip->i_height);
-	gfs2_alloc_get(ip);
+	if (!gfs2_alloc_get(ip))
+		return -ENOMEM;
 
 	error = gfs2_quota_hold(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
 	if (error)