linux-kernel - Re: [PATCH bpf-next] samples: bpf: fix conflicting types in fds

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Date:   Wed, 1 Dec 2021 14:31:00 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] samples: bpf: fix conflicting types in fds_example

On Wed, Dec 1, 2021 at 8:50 AM Alexander Lobakin
<alexandr.lobakin@...el.com> wrote:
>
> Fix the following samples/bpf build error appeared after the
> introduction of bpf_map_create() in libbpf:
>
>   CC  samples/bpf/fds_example.o
> samples/bpf/fds_example.c:49:12: error: static declaration of 'bpf_map_create' follows non-static declaration
> static int bpf_map_create(void)
>            ^
> samples/bpf/libbpf/include/bpf/bpf.h:55:16: note: previous declaration is here
> LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
>                ^
> samples/bpf/fds_example.c:82:23: error: too few arguments to function call, expected 6, have 0
>                 fd = bpf_map_create();
>                      ~~~~~~~~~~~~~~ ^
> samples/bpf/libbpf/include/bpf/bpf.h:55:16: note: 'bpf_map_create' declared here
> LIBBPF_API int bpf_map_create(enum bpf_map_type map_type,
>                ^
> 2 errors generated.
>
> fds_example by accident has a static function with the same name.
> It's not worth it to separate a single call into its own function,
> so just embed it.
>
> Fixes: 992c4225419a ("libbpf: Unify low-level map creation APIs w/ new bpf_map_create()")
> Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
> Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> ---
>  samples/bpf/fds_example.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/samples/bpf/fds_example.c b/samples/bpf/fds_example.c
> index 59f45fef5110..9a7c1fd7a4a8 100644
> --- a/samples/bpf/fds_example.c
> +++ b/samples/bpf/fds_example.c
> @@ -46,12 +46,6 @@ static void usage(void)
>         printf("       -h          Display this help.\n");
>  }
>
> -static int bpf_map_create(void)
> -{
> -       return bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(uint32_t),
> -                             sizeof(uint32_t), 1024, 0);
> -}
> -
>  static int bpf_prog_create(const char *object)
>  {
>         static struct bpf_insn insns[] = {
> @@ -79,7 +73,8 @@ static int bpf_do_map(const char *file, uint32_t flags, uint32_t key,
>         int fd, ret;
>
>         if (flags & BPF_F_PIN) {
> -               fd = bpf_map_create();
> +               fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(uint32_t),
> +                                   sizeof(uint32_t), 1024, 0);

Would be even better to use bpf_map_create() API instead, but that's
fine, I'm sending a big clean up patch for this and other uses of
deprecated APIs in samples/bpf. Applied to bpf-next.

>                 printf("bpf: map fd:%d (%s)\n", fd, strerror(errno));
>                 assert(fd > 0);
>
> --
> 2.33.1
>