kernfs: use lookup_one_len_unlocked()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/kernfs/mount.c

@@ -120,9 +120,8 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 		kntmp = find_next_ancestor(kn, knparent);
 		if (WARN_ON(!kntmp))
 			return ERR_PTR(-EINVAL);
-		mutex_lock(&d_inode(dentry)->i_mutex);
-		dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
-		mutex_unlock(&d_inode(dentry)->i_mutex);
+		dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
+					       strlen(kntmp->name));
 		dput(dentry);
 		if (IS_ERR(dtmp))
 			return dtmp;