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

From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>,
	Olivier Langlois <olivier@trillion01.com>,
	io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] io_uring: store back buffer in case of failure
Date: Wed, 16 Jun 2021 08:44:36 -0600	[thread overview]
Message-ID: <6bf916b4-ba6f-c401-9e8b-341f9a7b88f7@kernel.dk> (raw)
In-Reply-To: <af2f7aa0-271f-ba70-8c6b-f6c6118e6f1f@gmail.com>

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