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From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[email protected]>, [email protected]
Subject: Re: [PATCH liburing v5 2/2] test/splice: add basic splice tests
Date: Mon, 24 Feb 2020 21:39:21 +0300	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>


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On 24/02/2020 21:33, Jens Axboe wrote:
> 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

I've wanted for long to kill this weird behaviour, it should consume the whole
link. Can't imagine any userspace app handling all edge-case errors right...

> submit fails. I'll clean up that bit.

...I should have tested better. Thanks!

-- 
Pavel Begunkov


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  reply	other threads:[~2020-02-24 18:40 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-24 17:54 [PATCH v5 0/2] splice helpers + tests Pavel Begunkov
2020-02-24 17:55 ` [PATCH liburing v5 1/2] splice: add splice(2) helpers Pavel Begunkov
2020-02-24 17:55 ` [PATCH liburing v5 2/2] test/splice: add basic splice tests Pavel Begunkov
2020-02-24 18:23   ` Jens Axboe
2020-02-24 18:26     ` Pavel Begunkov
2020-02-24 18:33       ` Jens Axboe
2020-02-24 18:39         ` Pavel Begunkov [this message]
2020-02-24 18:41           ` Jens Axboe
2020-02-24 18:47             ` Pavel Begunkov
2020-02-24 19:30               ` Jens Axboe

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