On Mon, Jul 19, 2021 at 10:36 AM Martynas Pumputis [off-list ref] 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 <redacted>
---
 .../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;
+       }
+

[...]