Re: [PATCH v4 bpf-next 6/6] selftests/bpf: check that ->elem_count is non-zero for the hash map

[Anton Protopopov <aspsk@isovalent.com>]

On Wed, Jul 05, 2023 at 06:26:25PM -0700, Alexei Starovoitov wrote:
> On Wed, Jul 5, 2023 at 9:00 AM Anton Protopopov <aspsk@isovalent.com> wrote:
> >
> > Previous commits populated the ->elem_count per-cpu pointer for hash maps.
> > Check that this pointer is non-NULL in an existing map.
> >
> > Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
> > ---
> >  tools/testing/selftests/bpf/progs/map_ptr_kern.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/tools/testing/selftests/bpf/progs/map_ptr_kern.c b/tools/testing/selftests/bpf/progs/map_ptr_kern.c
> > index db388f593d0a..d6e234a37ccb 100644
> > --- a/tools/testing/selftests/bpf/progs/map_ptr_kern.c
> > +++ b/tools/testing/selftests/bpf/progs/map_ptr_kern.c
> > @@ -33,6 +33,7 @@ struct bpf_map {
> >         __u32 value_size;
> >         __u32 max_entries;
> >         __u32 id;
> > +       __s64 *elem_count;
> >  } __attribute__((preserve_access_index));
> >
> >  static inline int check_bpf_map_fields(struct bpf_map *map, __u32 key_size,
> > @@ -111,6 +112,8 @@ static inline int check_hash(void)
> >
> >         VERIFY(check_default_noinline(&hash->map, map));
> >
> > +       VERIFY(map->elem_count != NULL);
> > +
> 
> imo that's worse than no test.
> Just use kfunc here and get the real count?

Then, as I mentioned in the previous version, I will have to teach kfuncs to
recognize const_ptr_to_map args just for the sake of this selftest, while we
already testing all functionality in the new selftest for test_maps. So I would
just omit this one. Or am I missing something?