linux-kernel - Re: [PATCH bpf-next] libbpf: Add bpf_map__set

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Message-ID: <CAEf4BzZTJ__PKs6GiDccjC+pKbGFeck2AV8UJ+iJEcLPMkdjTA@mail.gmail.com>
Date:   Wed, 13 Jul 2022 22:54:01 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Joe Burton <jevburton@...gle.com>,
        Joe Burton <jevburton.kernel@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
        Jiri Olsa <jolsa@...nel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] libbpf: Add bpf_map__set_name()

On Wed, Jul 13, 2022 at 4:02 PM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> On Wed, Jul 13, 2022 at 3:32 PM Joe Burton <jevburton@...gle.com> wrote:
> >
> > > Asked you internally, but not sure I follow. Can you share more on why
> > > the following won't fix it for us:
> > >
> > > https://lore.kernel.org/bpf/OSZP286MB1725CEA1C95C5CB8E7CCC53FB8869@OSZP286MB1725.JPNP286.PROD.OUTLOOK.COM/
> > >
> > > ?
> > >
> > > The idea seems to be to get the supplied map name (from the obj)
> > > instead of using pin name? So why is it not enough?
> >
> > You're correct, this approach also resolves the issue. No need for this
> > new API.
>
> SG! New helper might still be useful, but I'm not sure how safe that
> is, given how much we use the name internally in libbpf
> (name/pin_path). So it might be safer to use Anquan's approach for
> now.
>
> Andrii, any concerns with [1] ? Should we pull that in?

I already applied [1]. I'm uncomfortable with bpf_map__set_name() in
general, because map name is tied into BTF and other things, so it
needs much more careful thinking how to support sudden map renames.
But given the problem was with bpf_map__reuse_fd(), I think [1] solves
it already.


>
> [1] https://lore.kernel.org/bpf/OSZP286MB1725CEA1C95C5CB8E7CCC53FB8869@OSZP286MB1725.JPNP286.PROD.OUTLOOK.COM/