On Sat Feb 28, 2026 at 2:11 AM EST, Hui Zhu wrote: > From: Hui Zhu <[email protected]> > > When back-porting test_progs to different kernel versions, I encountered > an issue where the test_cgroup_iter_memcg test would falsely pass even > when bpf_mem_cgroup_page_state() failed. > > This patch adds explicit checks to ensure bpf_mem_cgroup_page_state() > doesn't return -1 before validating the actual statistics values. > > Signed-off-by: Hui Zhu <[email protected]>
I'm a bit confused, what is the exact scenario where we read -1 for these stats? AFAICT bpf_mem_cgroup_page_state has to return -1 for them, and it turn this is possible if the idx we're passing is not valid - but the ones we do always should be. > --- > .../selftests/bpf/prog_tests/cgroup_iter_memcg.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c > b/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c > index 88fc3e83d2b7..9eadfbd3fdb9 100644 > --- a/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c > +++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c > @@ -53,6 +53,8 @@ static void test_anon(struct bpf_link *link, struct > memcg_query *memcg_query) > if (!ASSERT_OK(read_stats(link), "read stats")) > goto cleanup; > > + ASSERT_NEQ(memcg_query->nr_anon_mapped, (unsigned long)-1, > + "bpf_mem_cgroup_page_state NR_ANON_MAPPED"); > ASSERT_GT(memcg_query->nr_anon_mapped, 0, "final anon mapped val"); > > cleanup: > @@ -88,6 +90,10 @@ static void test_file(struct bpf_link *link, struct > memcg_query *memcg_query) > if (!ASSERT_OK(read_stats(link), "read stats")) > goto cleanup_map; > > + ASSERT_NEQ(memcg_query->nr_file_pages, (unsigned long)-1, > + "bpf_mem_cgroup_page_state NR_FILE_PAGES"); > + ASSERT_NEQ(memcg_query->nr_file_mapped, (unsigned long)-1, > + "bpf_mem_cgroup_page_state NR_FILE_MAPPED"); > ASSERT_GT(memcg_query->nr_file_pages, 0, "final file value"); > ASSERT_GT(memcg_query->nr_file_mapped, 0, "final file mapped value"); > > @@ -119,6 +125,8 @@ static void test_shmem(struct bpf_link *link, struct > memcg_query *memcg_query) > if (!ASSERT_OK(read_stats(link), "read stats")) > goto cleanup; > > + ASSERT_NEQ(memcg_query->nr_shmem, (unsigned long)-1, > + "bpf_mem_cgroup_page_state NR_SHMEM"); > ASSERT_GT(memcg_query->nr_shmem, 0, "final shmem value"); > > cleanup: > @@ -144,6 +152,8 @@ static void test_pgfault(struct bpf_link *link, struct > memcg_query *memcg_query) > if (!ASSERT_OK(read_stats(link), "read stats")) > goto cleanup; > > + ASSERT_NEQ(memcg_query->pgfault, (unsigned long)-1, > + "bpf_mem_cgroup_vm_events PGFAULT"); > ASSERT_GT(memcg_query->pgfault, 0, "final pgfault val"); > > cleanup:
