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From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Hengqi Chen <hengqi.chen@gmail.com>
Cc: bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>, Yonghong Song <yhs@fb.com>,
	john fastabend <john.fastabend@gmail.com>
Subject: Re: [PATCH bpf-next 1/2] libbpf: Support uniform BTF-defined key/value specification across all BPF maps
Date: Wed, 8 Sep 2021 21:26:01 -0700	[thread overview]
Message-ID: <CAEf4BzYfOGi9YLTWWprDtRCHWNpx00kJWHWQ7WbczUaUZi8HRA@mail.gmail.com> (raw)
In-Reply-To: <20210905100914.33007-1-hengqi.chen@gmail.com>

On Sun, Sep 5, 2021 at 3:09 AM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>
> A bunch of BPF maps do not support specifying types for key and value.

s/types/BTF types/, it's a bit confusing otherwise

> This is non-uniform and inconvenient[0]. Currently, libbpf uses a retry
> logic which removes BTF type IDs when BPF map creation failed. Instead
> of retrying, this commit recognizes those specialized map and removes

s/map/maps/

> BTF type IDs when creating BPF map.
>
>   [0] Closes: https://github.com/libbpf/libbpf/issues/355
>
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---

For patch sets consisting of two or more patches, we ask for a cover
letter, so for the next revision please provide a cover letter with an
overall description of what the series is about.

>  tools/lib/bpf/libbpf.c | 35 ++++++++++++++++++++---------------
>  1 file changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 88d8825fc6f6..7068c4d07337 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4613,6 +4613,26 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
>                         create_attr.inner_map_fd = map->inner_map_fd;
>         }
>
> +       if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY ||
> +           def->type == BPF_MAP_TYPE_STACK_TRACE ||
> +           def->type == BPF_MAP_TYPE_CGROUP_ARRAY ||
> +           def->type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
> +           def->type == BPF_MAP_TYPE_HASH_OF_MAPS ||
> +           def->type == BPF_MAP_TYPE_DEVMAP ||
> +           def->type == BPF_MAP_TYPE_SOCKMAP ||
> +           def->type == BPF_MAP_TYPE_CPUMAP ||
> +           def->type == BPF_MAP_TYPE_XSKMAP ||
> +           def->type == BPF_MAP_TYPE_SOCKHASH ||
> +           def->type == BPF_MAP_TYPE_QUEUE ||
> +           def->type == BPF_MAP_TYPE_STACK ||
> +           def->type == BPF_MAP_TYPE_DEVMAP_HASH) {
> +               create_attr.btf_fd = 0;
> +               create_attr.btf_key_type_id = 0;
> +               create_attr.btf_value_type_id = 0;
> +               map->btf_key_type_id = 0;
> +               map->btf_value_type_id = 0;
> +       }

Let's do this as a more succinct switch statement. Consider also
slightly rearranging entries to keep "related" map types together:
  - SOCKMAP + SOCKHASH
  - DEVMAP + DEVMAP_HASH + CPUMAP + XSKMAP

Thanks!


> +
>         if (obj->gen_loader) {
>                 bpf_gen__map_create(obj->gen_loader, &create_attr, is_inner ? -1 : map - obj->maps);
>                 /* Pretend to have valid FD to pass various fd >= 0 checks.
> @@ -4622,21 +4642,6 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
>         } else {
>                 map->fd = bpf_create_map_xattr(&create_attr);
>         }
> -       if (map->fd < 0 && (create_attr.btf_key_type_id ||
> -                           create_attr.btf_value_type_id)) {
> -               char *cp, errmsg[STRERR_BUFSIZE];
> -
> -               err = -errno;
> -               cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
> -               pr_warn("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n",
> -                       map->name, cp, err);
> -               create_attr.btf_fd = 0;
> -               create_attr.btf_key_type_id = 0;
> -               create_attr.btf_value_type_id = 0;
> -               map->btf_key_type_id = 0;
> -               map->btf_value_type_id = 0;
> -               map->fd = bpf_create_map_xattr(&create_attr);
> -       }
>

Please don't remove this fallback logic. There are multiple situations
where libbpf might need to retry map creation without BTF.

>         err = map->fd < 0 ? -errno : 0;
>
> --
> 2.25.1
>

  parent reply	other threads:[~2021-09-09  4:26 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-05 10:09 [PATCH bpf-next 1/2] libbpf: Support uniform BTF-defined key/value specification across all BPF maps Hengqi Chen
2021-09-05 10:09 ` [PATCH bpf-next 2/2] selftests/bpf: Test BPF map creation using BTF-defined key/value Hengqi Chen
2021-09-09  4:29   ` Andrii Nakryiko
2021-09-30 16:05     ` Hengqi Chen
2021-09-30 18:39       ` Andrii Nakryiko
2021-10-02 16:17         ` Hengqi Chen
2021-09-09  4:26 ` Andrii Nakryiko [this message]
2021-09-30 15:58   ` [PATCH bpf-next 1/2] libbpf: Support uniform BTF-defined key/value specification across all BPF maps Hengqi Chen
2021-09-30 16:14 [PATCH bpf-next 0/2] " Hengqi Chen
2021-09-30 16:14 ` [PATCH bpf-next 1/2] " Hengqi Chen

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