netdev - Re: [PATCH v2 0/4] open/accept directly into io

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Date:   Tue, 17 Aug 2021 10:33:03 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Stefan Metzmacher <metze@...ba.org>, Jens Axboe <axboe@...nel.dk>,
        io-uring@...r.kernel.org, Josh Triplett <josh@...htriplett.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 0/4] open/accept directly into io_uring fixed file
 table

On 8/16/21 4:45 PM, Stefan Metzmacher wrote:
> Hi Pavel,
> 
>> The behaviour is controlled by setting sqe->file_index, where 0 implies
>> the old behaviour. If non-zero value is specified, then it will behave
>> as described and place the file into a fixed file slot
>> sqe->file_index - 1. A file table should be already created, the slot
>> should be valid and empty, otherwise the operation will fail.
>>
>> Note 1: we can't use IOSQE_FIXED_FILE to switch between modes, because
>> accept takes a file, and it already uses the flag with a different
>> meaning.
> 
> Would it be hard to support IOSQE_FIXED_FILE for the dirfd of openat*, renameat, unlinkat, statx?
> (And mkdirat, linkat, symlinkat when they arrive)
> renameat and linkat might be trickier as they take two dirfds, but it
> would make the feature more complete and useful.

Good idea. There is nothing blocking on the io_uring side, but
the fs part may get ugly, e.g. too intrusive. We definitely need
to take a look

-- 
Pavel Begunkov