struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
{
	struct qstr this;
	unsigned int c;
	int err;

	WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));

	this.name = name;
	this.len = len;
	this.hash = full_name_hash(name, len);
	if (!len)
		return ERR_PTR(-EACCES);

	if (unlikely(name[0] == '.')) {
		if (len < 2 || (len == 2 && name[1] == '.'))
			return ERR_PTR(-EACCES);
	}

	while (len--) {
		c = *(const unsigned char *)name++;
		if (c == '/' || c == '\0')
			return ERR_PTR(-EACCES);
	}
	/*
	 * See if the low-level filesystem might want
	 * to use its own hash..
	 */
	if (base->d_flags & DCACHE_OP_HASH) {
		int err = base->d_op->d_hash(base, &this);
		if (err < 0)
			return ERR_PTR(err);
	}

	err = inode_permission(base->d_inode, MAY_EXEC);
	if (err)
		return ERR_PTR(err);

	return __lookup_hash(&this, base, 0);
}