ceph: always initialize the dentry in open_root_dentry()

When open_root_dentry() gets a dentry via d_obtain_alias() it does
not get initialized.  If the dentry obtained came from the cache,
this is OK.  But if not, the result is an improperly initialized
dentry.

To fix this, call ceph_init_dentry() regardless of which path
produced the dentry.  That function returns immediately for a dentry
that is already initialized, it is safe to use either way.

(Credit to Sage, who suggested this fix.)
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/ceph/super.c

@@ -638,12 +638,11 @@ static struct dentry *open_root_dentry(struct ceph_fs_client *fsc,
 	if (err == 0) {
 		dout("open_root_inode success\n");
 		if (ceph_ino(req->r_target_inode) == CEPH_INO_ROOT &&
-		    fsc->sb->s_root == NULL) {
+		    fsc->sb->s_root == NULL)
 			root = d_alloc_root(req->r_target_inode);
-			ceph_init_dentry(root);
-		} else {
+		else
 			root = d_obtain_alias(req->r_target_inode);
-		}
+		ceph_init_dentry(root);
 		req->r_target_inode = NULL;
 		dout("open_root_inode success, root dentry is %p\n", root);
 	} else {