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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Mon, 5 Jun 2023 15:07:21 -0700
Message-ID: <CAADnVQLZkUFtCwZEaRKMrdnDJzj-9_7fMYY9P55MndiNTrSnkA@mail.gmail.com>
Subject: Re: [PATCH bpf-next 2/2] selftests/bpf: Test bpf_for_each_map_elem on BPF_MAP_TYPE_HASH_OF_MAPS
To:     David Vernet <void@manifault.com>
Cc:     bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Kernel Team <kernel-team@meta.com>,
        Dave Marchevsky <davemarchevsky@meta.com>
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On Mon, Jun 5, 2023 at 1:05=E2=80=AFPM David Vernet <void@manifault.com> wr=
ote:
>
> +
> +static __u64 set_invoked(struct bpf_map *map, __u64 *key, __u64 *val, st=
ruct callback_ctx *ctx)
> +{
> +       struct bpf_map *inner_map;
> +
> +       ctx->invoked =3D true;
> +       inner_map =3D bpf_map_lookup_elem(map, key);
> +       if (!inner_map) {
> +               ctx->failed =3D true;
> +               return 1;
> +       }

This doesn't look right. 'val' is not 'u64 *'.
It probably should be 'struct bpf_map *',
so lookup shouldn't be necessary.

map_set_for_each_callback_args() just sets it to PTR_TO_MAP_VALUE.
It probably should be CONST_PTR_TO_MAP.
Also for normal hash map for_each_elem 'val' is writeable.
It shouldn't be in this case.
So to cleanly support iterating hash_of_maps patch 1 needs more work.