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From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Tue, 14 Jan 2020 10:36:40 -0800
Message-ID: <CAEf4BzYEGv-q7p0rK-d94Ng0fyQLuTEvsy1ZSzTdk0xZcyibQA@mail.gmail.com>
Subject: Re: [PATCH v4 bpf-next 7/9] libbpf: add libbpf support to batch ops
To:     Brian Vazquez <brianvv@google.com>
Cc:     Brian Vazquez <brianvv.kernel@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        "David S . Miller" <davem@davemloft.net>,
        Yonghong Song <yhs@fb.com>,
        Stanislav Fomichev <sdf@google.com>,
        Petar Penkov <ppenkov@google.com>,
        Willem de Bruijn <willemb@google.com>,
        open list <linux-kernel@vger.kernel.org>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
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On Tue, Jan 14, 2020 at 8:46 AM Brian Vazquez <brianvv@google.com> wrote:
>
> From: Yonghong Song <yhs@fb.com>
>
> Added four libbpf API functions to support map batch operations:
>   . int bpf_map_delete_batch( ... )
>   . int bpf_map_lookup_batch( ... )
>   . int bpf_map_lookup_and_delete_batch( ... )
>   . int bpf_map_update_batch( ... )
>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
>  tools/lib/bpf/bpf.c      | 60 ++++++++++++++++++++++++++++++++++++++++
>  tools/lib/bpf/bpf.h      | 22 +++++++++++++++
>  tools/lib/bpf/libbpf.map |  4 +++
>  3 files changed, 86 insertions(+)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 500afe478e94a..12ce8d275f7dc 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -452,6 +452,66 @@ int bpf_map_freeze(int fd)
>         return sys_bpf(BPF_MAP_FREEZE, &attr, sizeof(attr));
>  }
>
> +static int bpf_map_batch_common(int cmd, int fd, void  *in_batch,
> +                               void *out_batch, void *keys, void *values,
> +                               __u32 *count,
> +                               const struct bpf_map_batch_opts *opts)
> +{
> +       union bpf_attr attr = {};
> +       int ret;
> +
> +       if (!OPTS_VALID(opts, bpf_map_batch_opts))
> +               return -EINVAL;
> +
> +       memset(&attr, 0, sizeof(attr));
> +       attr.batch.map_fd = fd;
> +       attr.batch.in_batch = ptr_to_u64(in_batch);
> +       attr.batch.out_batch = ptr_to_u64(out_batch);
> +       attr.batch.keys = ptr_to_u64(keys);
> +       attr.batch.values = ptr_to_u64(values);
> +       if (count)
> +               attr.batch.count = *count;
> +       attr.batch.elem_flags  = OPTS_GET(opts, elem_flags, 0);
> +       attr.batch.flags = OPTS_GET(opts, flags, 0);
> +
> +       ret = sys_bpf(cmd, &attr, sizeof(attr));
> +       if (count)
> +               *count = attr.batch.count;

what if syscall failed, do you still want to assign *count then?

> +
> +       return ret;
> +}
> +

[...]