Re: [PATCH RFC] io_uring: remove retries from io_wq_submit_work()

[Pavel Begunkov <asml.silence@gmail.com>]

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On 24/02/2020 21:16, Jens Axboe wrote:
> On 2/24/20 8:40 AM, Pavel Begunkov wrote:
>> On 24/02/2020 18:27, Jens Axboe wrote:
>>> On 2/24/20 2:15 AM, Pavel Begunkov wrote:
>>>> It seems no opcode may return -EAGAIN for non-blocking case and expect
>>>> to be reissued. Remove retry code from io_wq_submit_work().
>>>
>>> There's actually a comment right there on how that's possible :-)
>>
>> Yeah, I saw it and understand the motive, and how it may happen, but can't
>> find a line, which can actually return -EAGAIN. Could you please point to an
>> example?
> 
> Just give it a whirl, should be easy to reproduce if you just do:
> 
> # echo 2 > /sys/block/nvme0n1/queue/nr_requests
> # fio/t/io_uring /dev/nvme0n1
> 
> or something like that. It's propagated from the kiocb endio handler,
> through, req->result at the bottom of io_issue_sqe()

I see now, thanks! What a jungle

> 
> 	if (ctx->flags & IORING_SETUP_IOPOLL) {
> 		const bool in_async = io_wq_current_is_worker();
> 
> 		if (req->result == -EAGAIN)                                     
> 			return -EAGAIN;
> 	[...]
> 
> 

-- 
Pavel Begunkov


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