netdev - Re: [PATCH v1 12/15] io_uring/zcrx: add io

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Message-ID: <d5be304b-0676-4f4e-adbc-eea3f7b161de@gmail.com>
Date: Wed, 9 Oct 2024 20:47:29 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Jens Axboe <axboe@...nel.dk>, David Wei <dw@...idwei.uk>,
 io-uring@...r.kernel.org, netdev@...r.kernel.org
Cc: Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>, David Ahern <dsahern@...nel.org>,
 Mina Almasry <almasrymina@...gle.com>
Subject: Re: [PATCH v1 12/15] io_uring/zcrx: add io_recvzc request

On 10/9/24 20:42, Jens Axboe wrote:
> On 10/9/24 1:27 PM, Pavel Begunkov wrote:
>>>>>> +    /* All data completions are posted as aux CQEs. */
>>>>>> +    req->flags |= REQ_F_APOLL_MULTISHOT;
>>>>>
>>>>> This puzzles me a bit...
>>>>
>>>> Well, it's a multishot request. And that flag protects from cq
>>>> locking rules violations, i.e. avoiding multishot reqs from
>>>> posting from io-wq.
>>>
>>> Maybe make it more like the others and require that
>>> IORING_RECV_MULTISHOT is set then, and set it based on that?
>>
>> if (IORING_RECV_MULTISHOT)
>>      return -EINVAL;
>> req->flags |= REQ_F_APOLL_MULTISHOT;
>>
>> It can be this if that's the preference. It's a bit more consistent,
>> but might be harder to use. Though I can just hide the flag behind
>> liburing helpers, would spare from neverending GH issues asking
>> why it's -EINVAL'ed
> 
> Maybe I'm missing something, but why not make it:
> 
> /* multishot required */
> if (!(flags & IORING_RECV_MULTISHOT))
> 	return -EINVAL;
> req->flags |= REQ_F_APOLL_MULTISHOT;

Right, that's what I meant before spewing a non sensible snippet.

> and yeah just put it in the io_uring_prep_recv_zc() or whatever helper.
> That would seem to be a lot more consistent with other users, no?

-- 
Pavel Begunkov