Re: [PATCH mptcp-next 3/3] selftests: mptcp: connect: trigger splice_eof

[Geliang Tang <geliang@kernel.org>]

Hi Matt,

On Mon, 2026-02-02 at 11:09 +0100, Matthieu Baerts wrote:
> Hi Geliang,
> 
> On 02/02/2026 10:21, Geliang Tang wrote:
> > From: Geliang Tang <tanggeliang@kylinos.cn>
> > 
> > Increase the sendfile count by one to ensure the transmission size
> > exceeds the actual data length. This triggers the splice_eof path
> > in the kernel, allowing the newly implemented MPTCP splice_eof
> > interface to be exercised during testing.
> > 
> > The change from 'count' to 'count + 1' forces the sendfile
> > operation
> > to attempt sending one more byte than available, which activates
> > the
> > end-of-file handling in the splicing logic and ensures coverage of
> > the related MPTCP code paths.
> 
> I'm a bit confused: is this splice_eof interface not linked to
> "splice"?
> Why is it used with sendfile()?

.splice_eof hook is indeed triggered by sendfile(), not by splice().

sendfile -> do_sendfile -> do_splice_direct -> do_splice_direct_actor
-> splice_direct_to_actor -> do_splice_eof.

> 
> Also, what's the behaviour without the implementation of
> "splice_eof()"?
> Was it a wrong behaviour or is it the same? What's the differences
> between the situation before and after this series?

Without 'splice_eof', it was no a wrong behaviour, but MPTCP didn't
previously handle the splice EOF notification. TCP handled it.

> 
> Cheers,
> Matt