rem: if(v != NULL) return v->id % range; else return (*key) % range;
add: if (vnode != NULL) return vnode->id % range;  return (*key) % range;
context: rootfs_vnode_hash_func(void *_v, const void *_key, unsigned int range){	struct rootfs_vnode *v = _v;	const vnode_id *key = _key;	if(v != NULL)		return v->id % range;	else		return (*key) % range;}