netdev - Re: [PATCH bpf-next 2/5] bpftool: Fix missing BTF output for json during map dump

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Date:   Tue, 14 Jan 2020 17:34:33 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Kernel Team <kernel-team@...com>,
        Networking <netdev@...r.kernel.org>,
        Paul Chaignon <paul.chaignon@...nge.com>
Subject: Re: [PATCH bpf-next 2/5] bpftool: Fix missing BTF output for json
 during map dump

On Tue, Jan 14, 2020 at 2:45 PM Martin KaFai Lau <kafai@...com> wrote:
>
> The btf availability check is only done for plain text output.
> It causes the whole BTF output went missing when json_output
> is used.
>
> This patch simplifies the logic a little by avoiding passing "int btf" to
> map_dump().
>
> For plain text output, the btf_wtr is only created when the map has
> BTF (i.e. info->btf_id != 0).  The nullness of "json_writer_t *wtr"
> in map_dump() alone can decide if dumping BTF output is needed.
> As long as wtr is not NULL, map_dump() will print out the BTF-described
> data whenever a map has BTF available (i.e. info->btf_id != 0)
> regardless of json or plain-text output.
>
> In do_dump(), the "int btf" is also renamed to "int do_plain_btf".
>
> Fixes: 99f9863a0c45 ("bpftool: Match maps by name")
> Cc: Paul Chaignon <paul.chaignon@...nge.com>
> Signed-off-by: Martin KaFai Lau <kafai@...com>
> ---

just one nit below

Acked-by: Andrii Nakryiko <andriin@...com>

>  tools/bpf/bpftool/map.c | 42 ++++++++++++++++++++---------------------
>  1 file changed, 20 insertions(+), 22 deletions(-)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index e00e9e19d6b7..45c1eda6512c 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -933,7 +933,7 @@ static int maps_have_btf(int *fds, int nb_fds)
>
>  static int
>  map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
> -        bool enable_btf, bool show_header)
> +        bool show_header)
>  {
>         void *key, *value, *prev_key;
>         unsigned int num_elems = 0;
> @@ -950,18 +950,16 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
>
>         prev_key = NULL;
>
> -       if (enable_btf) {
> -               err = btf__get_from_id(info->btf_id, &btf);
> -               if (err || !btf) {
> -                       /* enable_btf is true only if we've already checked
> -                        * that all maps have BTF information.
> -                        */
> -                       p_err("failed to get btf");
> -                       goto exit_free;
> +       if (wtr) {
> +               if (info->btf_id) {

combine into if (wtr && info->btf_id) and reduce nestedness?


> +                       err = btf__get_from_id(info->btf_id, &btf);
> +                       if (err || !btf) {
> +                               err = err ? : -ESRCH;
> +                               p_err("failed to get btf");
> +                               goto exit_free;
> +                       }

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