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

Jens Axboe
2025-03-21T11:15:02Z

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