Re: [PATCH bpf 2/2] selftests/bpf: check inner map deletion

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Mon, Jul 19, 2021 at 10:36 AM Martynas Pumputis <m@lambda.lt> wrote:
>
> Add a test case to check whether an unsuccessful creation of an outer
> map of a BTF-defined map-in-map destroys the inner map.
>
> As bpf_object__create_map() is a static function, we cannot just call it
> from the test case and then check whether a map accessible via
> map->inner_map_fd has been closed. Instead, we iterate over all maps and
> check whether the map "$MAP_NAME.inner" does not exist.
>
> Signed-off-by: Martynas Pumputis <m@lambda.lt>
> ---
>  .../bpf/progs/test_map_in_map_invalid.c       | 26 ++++++++
>  tools/testing/selftests/bpf/test_maps.c       | 64 ++++++++++++++++++-
>  2 files changed, 89 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/bpf/progs/test_map_in_map_invalid.c
>

[...]

> +       map = bpf_object__find_map_by_name(obj, "mim");
> +       if (!map) {
> +               printf("Failed to load array of maps from test prog\n");
> +               goto out_map_in_map;
> +       }
> +
> +       err = bpf_object__load(obj);

Hi Martynas,

This now is producing this warning, when running test_maps:

libbpf: map 'mim': failed to create: Invalid argument(-22)
libbpf: failed to load object './test_map_in_map_invalid.o'

It's quite confusing, I think it's better to mute this. You can do
that by temporarily swapping libbpf's logger function to a no-op
function, ignoring all the warnings. We do this in few other places,
see libbpf_set_print().

> +       if (!err) {
> +               printf("Loading obj supposed to fail\n");
> +               goto out_map_in_map;
> +       }
> +

[...]