Re: [PATCH bpf-next v2 0/5] libbpf: rename btf__get_from_id() and btf__load() APIs, support split BTF

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Quentin Monnet <quentin@isovalent.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next v2 0/5] libbpf: rename btf__get_from_id() and btf__load() APIs, support split BTF
Date: Fri, 23 Jul 2021 08:51:32 -0700	[thread overview]
Message-ID: <CAEf4BzYpCr=Vdfc3moaapQqBxYV3SKfD72s0F=FAh_zLzSqxqA@mail.gmail.com> (raw)
In-Reply-To: <82e61e60-e2e9-f42d-8e49-bbe416b7513d@isovalent.com>

On Fri, Jul 23, 2021 at 2:58 AM Quentin Monnet <quentin@isovalent.com> wrote:
>
> 2021-07-22 19:45 UTC-0700 ~ Andrii Nakryiko <andrii.nakryiko@gmail.com>
> > On Thu, Jul 22, 2021 at 5:58 PM Andrii Nakryiko
> > <andrii.nakryiko@gmail.com> wrote:
> >>
> >> On Wed, Jul 21, 2021 at 8:38 AM Quentin Monnet <quentin@isovalent.com> wrote:
> >>>
> >>> As part of the effort to move towards a v1.0 for libbpf [0], this set
> >>> improves some confusing function names related to BTF loading from and to
> >>> the kernel:
> >>>
> >>> - btf__load() becomes btf__load_into_kernel().
> >>> - btf__get_from_id becomes btf__load_from_kernel_by_id().
> >>> - A new version btf__load_from_kernel_by_id_split() extends the former to
> >>>   add support for split BTF.
> >>>
> >>> The old functions are not removed or marked as deprecated yet, there
> >>> should be in a future libbpf version.
> >>
> >> Oh, and I was thinking about this whole deprecation having to be done
> >> in two steps. It's super annoying to keep track of that. Ideally, we'd
> >> have some macro that can mark API deprecated "in the future", when
> >> actual libbpf version is >= to defined version. So something like
> >> this:
> >>
> >> LIBBPF_DEPRECATED_AFTER(V(0,5), "API that will be marked deprecated in v0.6")
> >
> > Better:
> >
> > LIBBPF_DEPRECATED_SINCE(0, 6, "API that will be marked deprecated in v0.6")
>
> I was considering a very advanced feature called “opening a new GitHub

Someone gotta track and ping people at the right time even with
issues, so yeah, it's suboptimal.

> issue” to track this :). But the macro game sounds interesting, I'll
> look into it for next version.
>
> One nit with LIBBPF_DEPRECATED_SINCE() is that the warning mentions a
> version (here v0.6) that we are unsure will exist (say we jump from v0.5
> to v1.0). But I don't suppose that's a real issue.

There will always be a +0.1 version just to get deprecation activated.
This is for the reason I explained: we add replacement API in 0.X, but
can mark deprecated API in 0.(X+1), so we won't skip it, even if we
have to wait 2 extra months before 1.0. So I wouldn't worry about
this.

>
> Thanks for the feedback!
> Quentin