 static ssize_t aio_setup_single_vector(struct kiocb *kiocb,
 				       int rw, char __user *buf,
 				       unsigned long *nr_segs,
 				       size_t len,
				       struct iovec *iovec,
				       struct iov_iter *iter)
 {
	if (len > MAX_RW_COUNT)
		len = MAX_RW_COUNT;
 	if (unlikely(!access_ok(!rw, buf, len)))
 		return -EFAULT;
 
 	iovec->iov_base = buf;
 	iovec->iov_len = len;
 	*nr_segs = 1;
	iov_iter_init(iter, rw, iovec, *nr_segs, len);
 	return 0;
 }

Unknown