linux-kernel - Re: [PATCH 1/2] iov: introduce ITER_BVEC_FLAG

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Message-ID: <ef3ddc2c-75ea-59aa-f27e-f974b003802e@gmail.com>
Date:   Sun, 13 Dec 2020 22:09:00 +0000
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Christoph Hellwig <hch@...radead.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>, Jens Axboe <axboe@...nel.dk>,
        linux-fsdevel@...r.kernel.org, io-uring@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] iov: introduce ITER_BVEC_FLAG_FIXED

On 09/12/2020 18:24, Matthew Wilcox wrote:
> On Wed, Dec 09, 2020 at 05:55:53PM +0000, Christoph Hellwig wrote:
>> On Wed, Dec 09, 2020 at 01:37:05PM +0000, Pavel Begunkov wrote:
>>> Yeah, I had troubles to put comments around, and it's still open.
>>>
>>> For current cases it can be bound to kiocb, e.g. "if an bvec iter passed
>>> "together" with kiocb then the vector should stay intact up to 
>>> ->ki_complete()". But that "together" is rather full of holes.
>>
>> What about: "For bvec based iters the bvec must not be freed until the
>> I/O has completed.  For asynchronous I/O that means it must be freed
>> no earlier than from ->ki_complete."
> 
> Perhaps for the second sentence "If the I/O is completed asynchronously,
> the bvec must not be freed before ->ki_complete() has been called"?

Sounds good, I'll use it. Thanks!

-- 
Pavel Begunkov