On 2/24/20 11:26 AM, Pavel Begunkov wrote:
> On 24/02/2020 21:23, Jens Axboe wrote:
>> On 2/24/20 10:55 AM, Pavel Begunkov wrote:
>>> +static int copy_single(struct io_uring *ring,
>>> + int fd_in, loff_t off_in,
>>> + int fd_out, loff_t off_out,
>>> + int pipe_fds[2],
>>> + unsigned int len,
>>> + unsigned flags1, unsigned flags2)
>>> +{
>>> + struct io_uring_cqe *cqe;
>>> + struct io_uring_sqe *sqe;
>>> + int i, ret = -1;
>>> +
>>> + sqe = io_uring_get_sqe(ring);
>>> + if (!sqe) {
>>> + fprintf(stderr, "get sqe failed\n");
>>> + return -1;
>>> + }
>>> + io_uring_prep_splice(sqe, fd_in, off_in, pipe_fds[1], -1,
>>> + len, flags1);
>>> + sqe->flags = IOSQE_IO_LINK;
>>> +
>>> + sqe = io_uring_get_sqe(ring);
>>> + if (!sqe) {
>>> + fprintf(stderr, "get sqe failed\n");
>>> + return -1;
>>> + }
>>> + io_uring_prep_splice(sqe, pipe_fds[0], -1, fd_out, off_out,
>>> + len, flags2);
>>> +
>>> + ret = io_uring_submit(ring);
>>> + if (ret <= 1) {
>>> + fprintf(stderr, "sqe submit failed: %d\n", ret);
>>> + return -1;
>>> + }
>>
>> This seems wrong, you prep one and submit, the right return value would
>> be 1. This check should be < 1, not <= 1. I'll make the change, rest
>> looks good to me. Thanks!
>>
>
> There are 2 sqes, "fd_in -> pipe" and "pipe -> fd_out".
I must be blind... I guess the failure case is that it doesn't work so well
on the kernels not supporting splice, as we'll return 1 there as the first
submit fails. I'll clean up that bit.
--
Jens Axboe
