gfs2: Initialize iopen glock holder for new inodes

In gfs2_init_inode_once, initialize inode->i_iopen_gh.gh_gl to NULL:
otherwise, when gfs2_inode_lookup fails, the iopen glock holder can
remain unset and iget_failed can end up accessing random memory.
Signed-off-by: NAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: NBob Peterson <rpeterso@redhat.com>

fs/gfs2/main.c

@@ -45,6 +45,7 @@ static void gfs2_init_inode_once(void *foo)
 	memset(&ip->i_res, 0, sizeof(ip->i_res));
 	RB_CLEAR_NODE(&ip->i_res.rs_node);
 	ip->i_hash_cache = NULL;
+	ip->i_iopen_gh.gh_gl = NULL;
 }
 
 static void gfs2_init_glock_once(void *foo)