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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Mon, 26 Jun 2023 14:59:35 -0700
Message-ID: <CAM9d7cgaXHU0=K-T80Vv6vh1pFyF=Jo-hgTrHXbOq5gpf5ux8w@mail.gmail.com>
Subject: Re: [PATCH net-next] tools: Fix MSG_SPLICE_PAGES build error in trace tools
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     Matthieu Baerts <matthieu.baerts@tessares.net>,
        David Howells <dhowells@redhat.com>, netdev@vger.kernel.org,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        David Miller <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Matthew Wilcox <willy@infradead.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        linux-perf-users@vger.kernel.org, bpf@vger.kernel.org,
        linux-next@vger.kernel.org, linux-kernel@vger.kernel.org
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On Mon, Jun 26, 2023 at 2:53 PM Jakub Kicinski <kuba@kernel.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@kernel.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.

Thanks,
Namhyung