linux-kernel - Re: [PATCH net-next] tools: Fix MSG_SPLICE

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Message-ID: <35d67fc65d5ff70c102040ce095a7c4a8b5da8bb.camel@redhat.com>
Date:   Tue, 27 Jun 2023 11:53:05 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Namhyung Kim <namhyung@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Matthieu Baerts <matthieu.baerts@...sares.net>,
        David Howells <dhowells@...hat.com>, netdev@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jens Axboe <axboe@...nel.dk>,
        Matthew Wilcox <willy@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, bpf@...r.kernel.org,
        linux-next@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] tools: Fix MSG_SPLICE_PAGES build error in
 trace tools

On Mon, 2023-06-26 at 14:59 -0700, Namhyung Kim wrote:
> On Mon, Jun 26, 2023 at 2:53 PM Jakub Kicinski <kuba@...nel.org> wrote:
> > 
> > On Mon, 26 Jun 2023 14:31:39 -0700 Namhyung Kim wrote:
> > > Right, we want to keep the headers files in the tools in sync with
> > > the kernel ones.  And they are used to generate some tables.
> > > Full explanation from Arnaldo below.
> > > 
> > > So I'm ok for the msg_flags.c changes, but please refrain from
> > > changing the header directly.  We will update it later.
> > > 
> > > With that,
> > >   Acked-by: Namhyung Kim <namhyung@...nel.org>
> > 
> > Ah, missed this email, sounds like this is preferred to Matthieu's
> > fix, we'll take this one.
> 
> Hmm.. I believe they are the same when it comes to the
> changes in the .c file.
> 
> > 
> > > Also I wonder if the tool needs to keep the original flag
> > > (SENDPAGE_NOTLAST) for the older kernels.
> > 
> > That's a bit unclear, because it's just a kernel-internal flag.
> > Future kernels may well use that bit for something else.
> 
> Ah, ok then.  I thought it's a user-visible flag.
> 
> > 
> > Better long term solution would be to use an enum so that the values
> > are included in debuginfo and perf can read them at runtime :(
> 
> Right, we also consider BTF to read the values and hopefully
> get rid of the business of copying kernel headers.

I read all the above as the preferred solution is the one provided by
Mat's patch (not touching socket.h, same changes as here in
msg_flags.c.

As such, I'll restore Mat's patch in PW and will obsolete this one.
Please raise a flag if I'm wrong ;)

Cheers,

Paolo