On Tue, Oct 29, 2019 at 12:39 PM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
>
> From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
>
> This adds support to libbpf for setting map pinning information as part of
> the BTF map declaration, to get automatic map pinning (and reuse) on load.
> The pinning type currently only supports a single PIN_BY_NAME mode, where
> each map will be pinned by its name in a path that can be overridden, but
> defaults to /sys/fs/bpf.
>
> Since auto-pinning only does something if any maps actually have a
> 'pinning' BTF attribute set, we default the new option to enabled, on the
> assumption that seamless pinning is what most callers want.
>
> When a map has a pin_path set at load time, libbpf will compare the map
> pinned at that location (if any), and if the attributes match, will re-use
> that map instead of creating a new one. If no existing map is found, the
> newly created map will instead be pinned at the location.
>
> Programs wanting to customise the pinning can override the pinning paths
> using bpf_map__set_pin_path() before calling bpf_object__load() (including
> setting it to NULL to disable pinning of a particular map).
>
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> ---
Please fix unconditional pin_path setting, with that:
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
> tools/lib/bpf/bpf_helpers.h | 6 ++
> tools/lib/bpf/libbpf.c | 144 +++++++++++++++++++++++++++++++++++++++++--
> tools/lib/bpf/libbpf.h | 13 ++++
> 3 files changed, 154 insertions(+), 9 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> index 2203595f38c3..0c7d28292898 100644
> --- a/tools/lib/bpf/bpf_helpers.h
> +++ b/tools/lib/bpf/bpf_helpers.h
> @@ -38,4 +38,10 @@ struct bpf_map_def {
> unsigned int map_flags;
> };
>
[...]
> @@ -1270,6 +1292,28 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
> }
> map->def.value_size = sz;
> map->btf_value_type_id = t->type;
> + } else if (strcmp(name, "pinning") == 0) {
> + __u32 val;
> + int err;
> +
> + if (!get_map_field_int(map_name, obj->btf, def, m,
> + &val))
> + return -EINVAL;
> + pr_debug("map '%s': found pinning = %u.\n",
> + map_name, val);
> +
> + if (val != LIBBPF_PIN_NONE &&
> + val != LIBBPF_PIN_BY_NAME) {
> + pr_warn("map '%s': invalid pinning value %u.\n",
> + map_name, val);
> + return -EINVAL;
> + }
> + err = build_map_pin_path(map, pin_root_path);
uhm... only if (val == LIBBPF_PIN_BY_NAME)?.. maybe extend tests with
a mix if auto-pinned and never pinned map to catch issue like this?
> + if (err) {
> + pr_warn("map '%s': couldn't build pin path.\n",
> + map_name);
> + return err;
> + }
> } else {
> if (strict) {
> pr_warn("map '%s': unknown field '%s'.\n",
> @@ -1289,7 +1333,8 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
> return 0;
> }
>
[...]
