ceph: clean up useless d_parent checks

d_parent is never NULL, and IS_ROOT() is the proper way to check for a
(non-self-referential) parent.
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Sage Weil <sage@inktank.com>

fs/ceph/dir.c

@@ -51,8 +51,7 @@ int ceph_init_dentry(struct dentry *dentry)
 		goto out_unlock;
 	}
 
-	if (dentry->d_parent == NULL ||   /* nfs fh_to_dentry */
-	    ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)
+	if (ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)
 		d_set_d_op(dentry, &ceph_dentry_ops);
 	else if (ceph_snap(dentry->d_parent->d_inode) == CEPH_SNAPDIR)
 		d_set_d_op(dentry, &ceph_snapdir_dentry_ops);
@@ -79,7 +78,7 @@ struct inode *ceph_get_dentry_parent_inode(struct dentry *dentry)
 		return NULL;
 
 	spin_lock(&dentry->d_lock);
-	if (dentry->d_parent) {
+	if (!IS_ROOT(dentry)) {
 		inode = dentry->d_parent->d_inode;
 		ihold(inode);
 	}
@@ -1140,7 +1139,7 @@ static void ceph_d_prune(struct dentry *dentry)
 	dout("ceph_d_prune %p\n", dentry);
 
 	/* do we have a valid parent? */
-	if (!dentry->d_parent || IS_ROOT(dentry))
+	if (IS_ROOT(dentry))
 		return;
 
 	/* if we are not hashed, we don't affect D_COMPLETE */

fs/ceph/mds_client.c

@@ -1469,11 +1469,6 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
 		else
 			len += 1 + temp->d_name.len;
 		temp = temp->d_parent;
-		if (temp == NULL) {
-			rcu_read_unlock();
-			pr_err("build_path corrupt dentry %p\n", dentry);
-			return ERR_PTR(-EINVAL);
-		}
 	}
 	rcu_read_unlock();
 	if (len)
@@ -1510,12 +1505,6 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
 		if (pos)
 			path[--pos] = '/';
 		temp = temp->d_parent;
-		if (temp == NULL) {
-			rcu_read_unlock();
-			pr_err("build_path corrupt dentry\n");
-			kfree(path);
-			return ERR_PTR(-EINVAL);
-		}
 	}
 	rcu_read_unlock();
 	if (pos != 0 || read_seqretry(&rename_lock, seq)) {