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

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Message-ID: <0fc1032f-908c-4e59-8f64-f22b380ae639@samba.org>
Date: Fri, 21 Mar 2025 08:55:58 +0100
From: Stefan Metzmacher <metze@...ba.org>
To: Pavel Begunkov <asml.silence@...il.com>, Jens Axboe <axboe@...nel.dk>,
 Joe Damato <jdamato@...tly.com>, Christoph Hellwig <hch@...radead.org>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 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
Cc: David Wei <dw@...idwei.uk>
Subject: Re: [RFC -next 00/10] Add ZC notifications to splice and sendfile

Am 20.03.25 um 11:46 schrieb Pavel Begunkov:
> On 3/19/25 19:15, Stefan Metzmacher wrote:
>> Am 19.03.25 um 19:37 schrieb Jens Axboe:
>>> On 3/19/25 11:45 AM, Joe Damato wrote:
>>>> On Wed, Mar 19, 2025 at 11:20:50AM -0600, Jens Axboe wrote:
> ...
>>> My argument would be the same as for other features - if you can do it
>>> simpler this other way, why not consider that? The end result would be
>>> the same, you can do fast sendfile() with sane buffer reuse. But the
>>> kernel side would be simpler, which is always a kernel main goal for
>>> those of us that have to maintain it.
>>>
>>> Just adding sendfile2() works in the sense that it's an easier drop in
>>> replacement for an app, though the error queue side does mean it needs
>>> to change anyway - it's not just replacing one syscall with another. And
>>> if we want to be lazy, sure that's fine. I just don't think it's the
>>> best way to do it when we literally have a mechanism that's designed for
>>> this and works with reuse already with normal send zc (and receive side
>>> too, in the next kernel).
>>
>> A few month (or even years) back, Pavel came up with an idea
>> to implement some kind of splice into a fixed buffer, if that
>> would be implemented I guess it would help me in Samba too.
>> My first usage was on the receive side (from the network).
> 
> I did it as a testing ground for infra needed for ublk zerocopy,
> but if that's of interest I can resurrect the patches and see
> where it goes, especially since the aforementioned infra just got
> queued.

Would be great!

Have you posted the work in progress somewhere?

Thanks!
metze