Re: [PATCH bpf-next] selftests/bpf: fix some bugs in map_lookup_percpu_elem testcase

[Andrii Nakryiko]

On Sun, May 15, 2022 at 7:25 PM Feng zhou <zhoufeng.zf@xxxxxxxxxxxxx> wrote:
>
> From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
>
> comments from Andrii Nakryiko, details in here:
> https://lore.kernel.org/lkml/20220511093854.411-1-zhoufeng.zf@xxxxxxxxxxxxx/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@xxxxxxxxxxxxx>
> ---
>  .../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 /* */

> +/* 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

>         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

> +               buf[i] = i;
> +       sum = (nr_cpus-1)*nr_cpus/2;

same, please follow kernel code style

> +
> +       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)

> +       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");

[...]