linux-kernel - Re: [External] Re: [PATCH bpf-next] selftests/bpf: fix some bugs in map_lookup_percpu

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Message-ID: <CAEf4BzabT5xdscH8jgTbAVhj415k=1MziKmAXTi6yfeo1DTBRw@mail.gmail.com>
Date:   Wed, 18 May 2022 21:38:28 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Feng Zhou <zhoufeng.zf@...edance.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
        Dave Marchevsky <davemarchevsky@...com>,
        Joanne Koong <joannekoong@...com>,
        Geliang Tang <geliang.tang@...e.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        duanxiongchun@...edance.com,
        Muchun Song <songmuchun@...edance.com>,
        Dongdong Wang <wangdongdong.6@...edance.com>,
        Cong Wang <cong.wang@...edance.com>,
        zhouchengming@...edance.com, Yosry Ahmed <yosryahmed@...gle.com>
Subject: Re: [External] Re: [PATCH bpf-next] selftests/bpf: fix some bugs in
 map_lookup_percpu_elem testcase

On Wed, May 18, 2022 at 8:27 PM Feng Zhou <zhoufeng.zf@...edance.com> wrote:
>
> 在 2022/5/19 上午8:17, Andrii Nakryiko 写道:
> > On Sun, May 15, 2022 at 7:25 PM Feng zhou <zhoufeng.zf@...edance.com> wrote:
> >> From: Feng Zhou <zhoufeng.zf@...edance.com>
> >>
> >> comments from Andrii Nakryiko, details in here:
> >> https://lore.kernel.org/lkml/20220511093854.411-1-zhoufeng.zf@bytedance.com/T/
> >>
> >> use /* */ instead of //
> >> use libbpf_num_possible_cpus() instead of sysconf(_SC_NPROCESSORS_ONLN)
> >> use 8 bytes for value size
> >> fix memory leak
> >> use ASSERT_EQ instead of ASSERT_OK
> >> add bpf_loop to fetch values on each possible CPU
> >>
> >> Fixes: ed7c13776e20c74486b0939a3c1de984c5efb6aa ("selftests/bpf: add test case for bpf_map_lookup_percpu_elem")
> >> Signed-off-by: Feng Zhou <zhoufeng.zf@...edance.com>
> >> ---
> >>   .../bpf/prog_tests/map_lookup_percpu_elem.c   | 49 +++++++++------
> >>   .../bpf/progs/test_map_lookup_percpu_elem.c   | 61 ++++++++++++-------
> >>   2 files changed, 70 insertions(+), 40 deletions(-)
> >>
> >> diff --git a/tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c b/tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c
> >> index 58b24c2112b0..89ca170f1c25 100644
> >> --- a/tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c
> >> +++ b/tools/testing/selftests/bpf/prog_tests/map_lookup_percpu_elem.c
> >> @@ -1,30 +1,39 @@
> >> -// SPDX-License-Identifier: GPL-2.0
> >> -// Copyright (c) 2022 Bytedance
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> > heh, so for SPDX license comment the rule is to use // in .c files :)
> > so keep SPDX as // and all others as /* */
>
> will do. Thanks.
>
> >
> >> +/* Copyright (c) 2022 Bytedance */
> >>
> >>   #include <test_progs.h>
> >>
> >>   #include "test_map_lookup_percpu_elem.skel.h"
> >>
> >> -#define TEST_VALUE  1
> >> -
> >>   void test_map_lookup_percpu_elem(void)
> >>   {
> >>          struct test_map_lookup_percpu_elem *skel;
> >> -       int key = 0, ret;
> >> -       int nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> >> -       int *buf;
> >> +       __u64 key = 0, sum;
> >> +       int ret, i;
> >> +       int nr_cpus = libbpf_num_possible_cpus();
> >> +       __u64 *buf;
> >>
> >> -       buf = (int *)malloc(nr_cpus*sizeof(int));
> >> +       buf = (__u64 *)malloc(nr_cpus*sizeof(__u64));
> > no need for casting
>
> casting means no '(__u64 *)'?
> just like this:
> 'buf = malloc(nr_cpus * sizeof(__u64));'
>

yes, in C you don't need to explicitly cast void * to other pointer types

> >
> >>          if (!ASSERT_OK_PTR(buf, "malloc"))
> >>                  return;
> >> -       memset(buf, 0, nr_cpus*sizeof(int));
> >> -       buf[0] = TEST_VALUE;
> >>
> >> -       skel = test_map_lookup_percpu_elem__open_and_load();
> >> -       if (!ASSERT_OK_PTR(skel, "test_map_lookup_percpu_elem__open_and_load"))
> >> -               return;
> >> +       for (i=0; i<nr_cpus; i++)
> > spaces between operators
>
> will do. Thanks.
>
> >
> >> +               buf[i] = i;
> >> +       sum = (nr_cpus-1)*nr_cpus/2;
> > same, please follow kernel code style
>
> will do. Thanks.
>
> >
> >> +
> >> +       skel = test_map_lookup_percpu_elem__open();
> >> +       if (!ASSERT_OK_PTR(skel, "test_map_lookup_percpu_elem__open"))
> >> +               goto exit;
> >> +
> > nit: keep it simple, init skel to NULL and use single cleanup goto
> > label that will destroy skel unconditionally (it deals with NULL just
> > fine)
>
> will do. Thanks.
>
> >> +       skel->rodata->nr_cpus = nr_cpus;
> >> +
> >> +       ret = test_map_lookup_percpu_elem__load(skel);
> >> +       if (!ASSERT_OK(ret, "test_map_lookup_percpu_elem__load"))
> >> +               goto cleanup;
> >> +
> >>          ret = test_map_lookup_percpu_elem__attach(skel);
> >> -       ASSERT_OK(ret, "test_map_lookup_percpu_elem__attach");
> >> +       if (!ASSERT_OK(ret, "test_map_lookup_percpu_elem__attach"))
> >> +               goto cleanup;
> >>
> >>          ret = bpf_map_update_elem(bpf_map__fd(skel->maps.percpu_array_map), &key, buf, 0);
> >>          ASSERT_OK(ret, "percpu_array_map update");
> > [...]
>
>