Re: [PATCH 3/3] io_uring/rw: add support for IORING_OP_READ_MULTISHOT

[Jens Axboe <axboe@kernel.dk>]

On 9/11/23 6:46 PM, Jens Axboe wrote:
>>> +	ret = __io_read(req, issue_flags);
>>> +
>>> +	/*
>>> +	 * If we get -EAGAIN, recycle our buffer and just let normal poll
>>> +	 * handling arm it.
>>> +	 */
>>> +	if (ret == -EAGAIN) {
>>> +		io_kbuf_recycle(req, issue_flags);
>>> +		return -EAGAIN;
>>> +	}
>>> +
>>> +	/*
>>> +	 * Any error will terminate a multishot request
>>> +	 */
>>> +	if (ret <= 0) {
>>> +finish:
>>> +		io_req_set_res(req, ret, cflags);
>>> +		if (issue_flags & IO_URING_F_MULTISHOT)
>>> +			return IOU_STOP_MULTISHOT;
>>> +		return IOU_OK;
>>
>> Just a style detail, but I'd prefer to unfold this on the end of the
>> function instead of jumping backwards here..
> 
> Sure, that might look better. I'll make the edit.

Actually we can just indent the next case and get rid of the goto
completely:

int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags)
{
	unsigned int cflags = 0;
	int ret;

	/*
	 * Multishot MUST be used on a pollable file
	 */
	if (!file_can_poll(req->file))
		return -EBADFD;

	ret = __io_read(req, issue_flags);

	/*
	 * If we get -EAGAIN, recycle our buffer and just let normal poll
	 * handling arm it.
	 */
	if (ret == -EAGAIN) {
		io_kbuf_recycle(req, issue_flags);
		return -EAGAIN;
	}

	/*
	 * Any successful return value will keep the multishot read armed.
	 */
	if (ret > 0) {
		/*
		 * Put our buffer and post a CQE. If we fail to post a CQE, then
		 * jump to the termination path. This request is then done.
		 */
		cflags = io_put_kbuf(req, issue_flags);

		if (io_fill_cqe_req_aux(req,
					issue_flags & IO_URING_F_COMPLETE_DEFER,
					ret, cflags | IORING_CQE_F_MORE)) {
			if (issue_flags & IO_URING_F_MULTISHOT)
				return IOU_ISSUE_SKIP_COMPLETE;
			return -EAGAIN;
		}
	}

	/*
	 * Either an error, or we've hit overflow posting the CQE. For any
	 * multishot request, hitting overflow will terminate it.
	 */
	io_req_set_res(req, ret, cflags);
	if (issue_flags & IO_URING_F_MULTISHOT)
		return IOU_STOP_MULTISHOT;
	return IOU_OK;
}

-- 
Jens Axboe