linux-kernel - Re: [RFC -next 00/10] Add ZC notifications to splice and sendfile

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Message-ID: <ca1fbeba-b749-4c34-b4be-c80056eccc3a@kernel.dk>
Date: Fri, 21 Mar 2025 05:14:59 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Christoph Hellwig <hch@...radead.org>, Joe Damato <jdamato@...tly.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 asml.silence@...il.com, linux-fsdevel@...r.kernel.org, edumazet@...gle.com,
 pabeni@...hat.com, horms@...nel.org, linux-api@...r.kernel.org,
 linux-arch@...r.kernel.org, viro@...iv.linux.org.uk, jack@...e.cz,
 kuba@...nel.org, shuah@...nel.org, sdf@...ichev.me, mingo@...hat.com,
 arnd@...db.de, brauner@...nel.org, akpm@...ux-foundation.org,
 tglx@...utronix.de, jolsa@...nel.org, linux-kselftest@...r.kernel.org
Subject: Re: [RFC -next 00/10] Add ZC notifications to splice and sendfile

On 3/20/25 11:56 PM, Christoph Hellwig wrote:
>> I don't know the entire historical context, but I presume sendmsg
>> did that because there was no other mechanism at the time.
> 
> At least aio had been around for about 15 years at the point, but
> networking folks tend to be pretty insular and reinvent things.

Yep...

>> It seems like Jens suggested that plumbing this through for splice
>> was a possibility, but sounds like you disagree.
> 
> Yes, very strongly.

And that is very much not what I suggested, fwiw.

>> As mentioned above and in other messages, it seems like it is
>> possible to improve the networking parts of splice (and therefore
>> sendfile) to make them safer to use without introducing a new system
>> call.
>>
>> Are you saying that you are against doing that, even if the code is
>> network specific (but lives in fs/)?
> 
> Yes.
> 
> Please take the work and integrate it with the kiocb-based system
> we use for all other in-kernel I/O that needs completion notifications
> and which makes it trivial to integate with io_uring instead of
> spreading an imcompatible and inferior event system.

Exactly, this is how we do async IO elsewhere, not sure why networking
needs to be special here, and definitely not special in a good way.

-- 
Jens Axboe