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Sat, 28 Feb 2026 13:50:18 -0800 (PST) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Sat, 28 Feb 2026 16:50:14 -0500 Message-Id: Subject: Re: [PATCH bpf-next v3 3/3] selftests/bpf: Check bpf_mem_cgroup_page_state return value From: "Emil Tsalapatis" To: "Hui Zhu" , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Martin KaFai Lau" , "Eduard Zingerman" , "Song Liu" , "Yonghong Song" , "John Fastabend" , "KP Singh" , "Stanislav Fomichev" , "Hao Luo" , "Jiri Olsa" , "Shuah Khan" , "JP Kobryn" , "Roman Gushchin" , , , Cc: "Hui Zhu" X-Mailer: aerc 0.20.1 References: In-Reply-To: On Sat Feb 28, 2026 at 2:11 AM EST, Hui Zhu wrote: > From: Hui Zhu > > 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 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.=20 > --- > .../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 mem= cg_query *memcg_query) > if (!ASSERT_OK(read_stats(link), "read stats")) > goto cleanup; > =20 > + 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"); > =20 > cleanup: > @@ -88,6 +90,10 @@ static void test_file(struct bpf_link *link, struct me= mcg_query *memcg_query) > if (!ASSERT_OK(read_stats(link), "read stats")) > goto cleanup_map; > =20 > + 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"); > =20 > @@ -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; > =20 > + 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"); > =20 > cleanup: > @@ -144,6 +152,8 @@ static void test_pgfault(struct bpf_link *link, struc= t memcg_query *memcg_query) > if (!ASSERT_OK(read_stats(link), "read stats")) > goto cleanup; > =20 > + ASSERT_NEQ(memcg_query->pgfault, (unsigned long)-1, > + "bpf_mem_cgroup_vm_events PGFAULT"); > ASSERT_GT(memcg_query->pgfault, 0, "final pgfault val"); > =20 > cleanup: