netdev - Re: [PATCH bpf-next] selftests/bpf: convert bpf_iter_test_kern{3,4}.c to define own bpf_iter

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Message-ID: <CAEf4Bzb2kLKHAVSO10yo1JO-Ye89XEz64eJh7cBkd3utXC3bkw@mail.gmail.com>
Date:   Tue, 19 May 2020 14:11:04 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next] selftests/bpf: convert bpf_iter_test_kern{3,4}.c
 to define own bpf_iter_meta

On Tue, May 19, 2020 at 2:08 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Tue, May 19, 2020 at 12:23:41PM -0700, Andrii Nakryiko wrote:
> > b9f4c01f3e0b ("selftest/bpf: Make bpf_iter selftest compilable against old vmlinux.h")
> > missed the fact that bpf_iter_test_kern{3,4}.c are not just including
> > bpf_iter_test_kern_common.h and need similar bpf_iter_meta re-definition
> > explicitly.
> >
> > Fixes: b9f4c01f3e0b ("selftest/bpf: Make bpf_iter selftest compilable against old vmlinux.h")
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > ---
> >  .../selftests/bpf/progs/bpf_iter_test_kern3.c     | 15 +++++++++++++++
> >  .../selftests/bpf/progs/bpf_iter_test_kern4.c     | 15 +++++++++++++++
> >  2 files changed, 30 insertions(+)
> >
> > diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_test_kern3.c b/tools/testing/selftests/bpf/progs/bpf_iter_test_kern3.c
> > index 636a00fa074d..13c2c90c835f 100644
> > --- a/tools/testing/selftests/bpf/progs/bpf_iter_test_kern3.c
> > +++ b/tools/testing/selftests/bpf/progs/bpf_iter_test_kern3.c
> > @@ -1,10 +1,25 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  /* Copyright (c) 2020 Facebook */
> > +#define bpf_iter_meta bpf_iter_meta___not_used
> > +#define bpf_iter__task bpf_iter__task___not_used
> >  #include "vmlinux.h"
> > +#undef bpf_iter_meta
> > +#undef bpf_iter__task
> >  #include <bpf/bpf_helpers.h>
> >
> >  char _license[] SEC("license") = "GPL";
> >
> > +struct bpf_iter_meta {
> > +     struct seq_file *seq;
> > +     __u64 session_id;
> > +     __u64 seq_num;
> > +} __attribute__((preserve_access_index));
> > +
> > +struct bpf_iter__task {
> > +     struct bpf_iter_meta *meta;
> > +     struct task_struct *task;
> > +} __attribute__((preserve_access_index));
>
> Applied, but I was wondering whether all these structs can be placed
> in a single header file like bpf_iters.h ?
> struct bpf_iter_meta is common across all of them.
> What if next iter patch changes the name in there?
> We'd need to patch 10 tests? It's unstable api, so it's fine,
> but considering the churn it seems common header would be good.
> That .h would include struct bpf_iter__bpf_map, bpf_iter__task,
> bpf_iter__task_file, etc
> wdyt?

I initially wanted to keep each selftest independent, so that anyone
looking for example would just have everything in one file. But I
agree, we have quite a bunch of them already, so it makes sense to
centralize that in one common header. I'll post a follow-up patch a
bit later to consolidate this.