linux-kernel - Re: [PATCH] io_uring: store back buffer in case of failure

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Message-ID: <6bf916b4-ba6f-c401-9e8b-341f9a7b88f7@kernel.dk>
Date:   Wed, 16 Jun 2021 08:44:36 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>,
        Olivier Langlois <olivier@...llion01.com>,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] io_uring: store back buffer in case of failure

On 6/16/21 8:01 AM, Pavel Begunkov wrote:
> On 6/16/21 2:42 PM, Olivier Langlois wrote:
>> On Tue, 2021-06-15 at 15:51 -0600, Jens Axboe wrote:
>>> Ditto for this one, don't see it in my email nor on the list.
>>>
>> I can resend you a private copy of this one but as Pavel pointed out,
>> it contains fatal flaws.
>>
>> So unless someone can tell me that the idea is interesting and has
>> potential and can give me some a hint or 2 about how to address the
>> challenges to fix the current flaws, it is pretty much a show stopper
>> to me and I think that I am going to let it go...
> 
> It'd need to go through some other context, e.g. task context.
> task_work_add() + custom handler would work, either buf-select
> synchronisation can be reworked, but both would rather be
> bulky and not great.

Indeed - that'd solve both the passing around of locking state which
I really don't like, and make it much simpler. Just use task work for
the re-insert, and you can grab the ring lock unconditionally from
there.

-- 
Jens Axboe