netdev - Re: [PATCH v2 bpf-next 3/3] libbpf: add BTF-defined map-in-map support

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Date:   Tue, 28 Apr 2020 11:03:36 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Andrii Nakryiko <andriin@...com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...com,
        daniel@...earbox.net, toke@...hat.com, andrii.nakryiko@...il.com,
        kernel-team@...com
Subject: Re: [PATCH v2 bpf-next 3/3] libbpf: add BTF-defined map-in-map
 support

On Mon, Apr 27, 2020 at 11:41:39PM -0700, Andrii Nakryiko wrote:
> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> index 60aad054eea1..e3a6e9a1f5b4 100644
> --- a/tools/lib/bpf/bpf_helpers.h
> +++ b/tools/lib/bpf/bpf_helpers.h
> @@ -12,6 +12,7 @@
>  
>  #define __uint(name, val) int (*name)[val]
>  #define __type(name, val) typeof(val) *name
> +#define __inner(name, val) typeof(val) *name[]
...
> +++ b/tools/testing/selftests/bpf/progs/test_btf_map_in_map.c
> @@ -0,0 +1,76 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (c) 2020 Facebook */
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +struct inner_map {
> +	__uint(type, BPF_MAP_TYPE_ARRAY);
> +	__uint(max_entries, 1);
> +	__type(key, int);
> +	__type(value, int);
> +} inner_map1 SEC(".maps"),
> +  inner_map2 SEC(".maps");
> +
> +struct outer_arr {
> +	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
> +	__uint(max_entries, 3);
> +	__uint(key_size, sizeof(int));
> +	__uint(value_size, sizeof(int));
> +	/* it's possible to use anonymous struct as inner map definition here */
> +	__inner(values, struct {
> +		__uint(type, BPF_MAP_TYPE_ARRAY);
> +		/* changing max_entries to 2 will fail during load
> +		 * due to incompatibility with inner_map definition */
> +		__uint(max_entries, 1);
> +		__type(key, int);
> +		__type(value, int);
> +	});

How about renaming it s/__inner/__array/ ?
Because that's what it defines from BTF pov.