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Subject: Re: [RFC 0/4] open/accept directly into io_uring fixed file table
To:     Stefan Metzmacher <metze@samba.org>,
        Pavel Begunkov <asml.silence@gmail.com>,
        io-uring@vger.kernel.org
Cc:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, Josh Triplett <josh@joshtriplett.org>
References: <cover.1625657451.git.asml.silence@gmail.com>
 <48bd91bc-ba1a-1e69-03a1-3d6f913f96c3@kernel.dk>
 <4accdfa5-36fc-7de8-f4b2-7609b6f9d8ee@samba.org>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <6db18003-bb72-daf7-f5e6-20f9e128ada3@kernel.dk>
Date:   Wed, 7 Jul 2021 09:01:47 -0600
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On 7/7/21 7:59 AM, Stefan Metzmacher wrote:
> Am 07.07.21 um 15:07 schrieb Jens Axboe:
>> On 7/7/21 5:39 AM, Pavel Begunkov wrote:
>>> Implement an old idea allowing open/accept io_uring requests to register
>>> a newly created file as a io_uring's fixed file instead of placing it
>>> into a task's file table. The switching is encoded in io_uring's SQEs
>>> by setting sqe->buf_index/file_index, so restricted to 2^16-1. Don't
>>> think we need more, but may be a good idea to scrap u32 somewhere
>>> instead.
>>>
>>> From the net side only needs a function doing __sys_accept4_file()
>>> but not installing fd, see 2/4.
>>>
>>> Only RFC for now, the new functionality is tested only for open yet.
>>> I hope we can remember the author of the idea to add attribution.
>>
>> Pretty sure the original suggester of this as Josh, CC'ed.
> 
> I also requested it for open :-)

Indeed! I honestly forget the details, as some of it is implementation
detail. I think Josh was the first to suggest a private fd table could
be used, but that's mostly implementation detail as the point was to be
able to know which fd would be assigned.

But I think we're all in agreement here, it's a nifty feature :-)

-- 
Jens Axboe