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

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Message-ID: <32a05d6b-1b82-467f-ac3e-f3cd2e5c0e22@kernel.dk>
Date: Wed, 9 Oct 2024 13:50:59 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Pavel Begunkov <asml.silence@...il.com>, 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 1:47 PM, Pavel Begunkov wrote:
> 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.

ok phew, I was scratching my head there for a bit... All good then.

-- 
Jens Axboe