rem: struct vnode *vnode = descriptor->vnode;
add: struct vnode *vnode = descriptor->u.vnode;
context: dir_rewind(struct file_descriptor *descriptor){	struct vnode *vnode = descriptor->vnode;	if (FS_CALL(vnode, rewind_dir))		return FS_CALL(vnode, rewind_dir)(vnode->mount->cookie,vnode->private_node,descriptor->cookie);	return EOPNOTSUPP;}