static void d_walk(struct dentry *parent, void *data,
		   enum d_walk_ret (*enter)(void *, struct dentry *),
		   void (*finish)(void *))
{
	struct dentry *this_parent;
	struct list_head *next;
	unsigned seq = 0;
	enum d_walk_ret ret;
	bool retry = true;

again:
	read_seqbegin_or_lock(&rename_lock, &seq);
	this_parent = parent;
	spin_lock(&this_parent->d_lock);

	ret = enter(data, this_parent);
	switch (ret) {
	case D_WALK_CONTINUE:
		break;
	case D_WALK_QUIT:
	case D_WALK_SKIP:
		goto out_unlock;
	case D_WALK_NORETRY:
		retry = false;
		break;
	}
repeat:
	next = this_parent->d_subdirs.next;
resume:
	while (next != &this_parent->d_subdirs) {
		struct list_head *tmp = next;
		struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
		next = tmp->next;

		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);

		ret = enter(data, dentry);
		switch (ret) {
		case D_WALK_CONTINUE:
			break;
		case D_WALK_QUIT:
			spin_unlock(&dentry->d_lock);
			goto out_unlock;
		case D_WALK_NORETRY:
			retry = false;
			break;
		case D_WALK_SKIP:
			spin_unlock(&dentry->d_lock);
			continue;
		}

		if (!list_empty(&dentry->d_subdirs)) {
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
			this_parent = dentry;
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
			goto repeat;
		}
		spin_unlock(&dentry->d_lock);
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	rcu_read_lock();
ascend:
	if (this_parent != parent) {
		struct dentry *child = this_parent;
		this_parent = child->d_parent;

		spin_unlock(&child->d_lock);
		spin_lock(&this_parent->d_lock);

		/* might go back up the wrong parent if we have had a rename. */
		if (need_seqretry(&rename_lock, seq))
			goto rename_retry;
		/* go into the first sibling still alive */
		do {
			next = child->d_child.next;
			if (next == &this_parent->d_subdirs)
				goto ascend;
			child = list_entry(next, struct dentry, d_child);
		} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
		rcu_read_unlock();
		goto resume;
	}
	if (need_seqretry(&rename_lock, seq))
		goto rename_retry;
	rcu_read_unlock();
	if (finish)
		finish(data);

out_unlock:
	spin_unlock(&this_parent->d_lock);
	done_seqretry(&rename_lock, seq);
	return;

rename_retry:
	spin_unlock(&this_parent->d_lock);
	rcu_read_unlock();
	BUG_ON(seq & 1);
	if (!retry)
		return;
	seq = 1;
	goto again;
}

This label identifies security gaps where expected security features are missing or only partially implemented, reducing protection against unauthorized access or manipulation.