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

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Date:   Thu, 19 May 2022 15:31:29 +0800
From:   Feng Zhou <zhoufeng.zf@...edance.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.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

在 2022/5/19 下午12:38, Andrii Nakryiko 写道:
> 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

Ok, Thanks.

>
>>>>           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");
>>> [...]
>>