[RFC PATCH bpf-next v3 11/12] selftests/bpf: Add test for memcg_bpf_ops hierarchies
From: Hui Zhu <hidden>
Date: 2026-01-23 09:02:42
Also in:
bpf, cgroups, linux-kselftest, linux-mm, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
From: Hui Zhu <redacted> Add a new selftest, `test_memcg_ops_hierarchies`, to validate the behavior of attaching `memcg_bpf_ops` in a nested cgroup hierarchy, specifically testing the `BPF_F_ALLOW_OVERRIDE` flag. The test case performs the following steps: 1. Creates a three-level deep cgroup hierarchy: `/cg`, `/cg/cg`, and `/cg/cg/cg`. 2. Attaches a BPF struct_ops to the top-level cgroup (`/cg`) with the `BPF_F_ALLOW_OVERRIDE` flag. 3. Successfully attaches a new struct_ops to the middle cgroup (`/cg/cg`) without the flag, overriding the inherited one. 4. Asserts that attaching another struct_ops to the deepest cgroup (`/cg/cg/cg`) fails with -EBUSY, because its parent did not specify `BPF_F_ALLOW_OVERRIDE`. This test ensures that the attachment logic correctly enforces the override rules across a cgroup subtree. Signed-off-by: Geliang Tang <geliang@kernel.org> Signed-off-by: Hui Zhu <redacted> --- .../selftests/bpf/prog_tests/memcg_ops.c | 69 +++++++++++++++++++ 1 file changed, 69 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/memcg_ops.c b/tools/testing/selftests/bpf/prog_tests/memcg_ops.c
index 9a8d16296f2d..bab9f3094f59 100644
--- a/tools/testing/selftests/bpf/prog_tests/memcg_ops.c
+++ b/tools/testing/selftests/bpf/prog_tests/memcg_ops.c@@ -535,3 +535,72 @@ void test_memcg_ops_below_min_over_high(void) close(low_cgroup_fd); cleanup_cgroup_environment(); } + +void test_memcg_ops_hierarchies(void) +{ + int ret, first = -1, second = -1, third = -1; + struct memcg_ops *skel; + struct bpf_map *map; + struct bpf_link *link1 = NULL, *link2 = NULL, *link3 = NULL; + DECLARE_LIBBPF_OPTS(bpf_struct_ops_opts, opts); + + ret = setup_cgroup_environment(); + if (!ASSERT_OK(ret, "setup_cgroup_environment")) + goto cleanup; + + first = create_and_get_cgroup("/cg"); + if (!ASSERT_GE(first, 0, "create_and_get_cgroup /cg")) + goto cleanup; + ret = enable_controllers("/cg", "memory"); + if (!ASSERT_OK(ret, "enable_controllers")) + goto cleanup; + + second = create_and_get_cgroup("/cg/cg"); + if (!ASSERT_GE(second, 0, "create_and_get_cgroup /cg/cg")) + goto cleanup; + ret = enable_controllers("/cg/cg", "memory"); + if (!ASSERT_OK(ret, "enable_controllers")) + goto cleanup; + + third = create_and_get_cgroup("/cg/cg/cg"); + if (!ASSERT_GE(third, 0, "create_and_get_cgroup /cg/cg/cg")) + goto cleanup; + ret = enable_controllers("/cg/cg/cg", "memory"); + if (!ASSERT_OK(ret, "enable_controllers")) + goto cleanup; + + skel = memcg_ops__open_and_load(); + if (!ASSERT_OK_PTR(skel, "memcg_ops__open_and_load")) + goto cleanup; + + map = bpf_object__find_map_by_name(skel->obj, "low_mcg_ops"); + if (!ASSERT_OK_PTR(map, "bpf_object__find_map_by_name low_mcg_ops")) + goto cleanup; + + opts.relative_fd = first; + opts.flags = BPF_F_ALLOW_OVERRIDE; + link1 = bpf_map__attach_struct_ops_opts(map, &opts); + if (!ASSERT_OK_PTR(link1, "bpf_map__attach_struct_ops_opts")) + goto cleanup; + + opts.relative_fd = second; + opts.flags = 0; + link2 = bpf_map__attach_struct_ops_opts(map, &opts); + if (!ASSERT_OK_PTR(link2, "bpf_map__attach_struct_ops_opts")) + goto cleanup; + + opts.relative_fd = third; + opts.flags = 0; + link2 = bpf_map__attach_struct_ops_opts(map, &opts); + if (!ASSERT_ERR_PTR(link3, "bpf_map__attach_struct_ops_opts")) + goto cleanup; + +cleanup: + bpf_link__destroy(link1); + bpf_link__destroy(link2); + memcg_ops__detach(skel); + close(first); + close(second); + close(third); + cleanup_cgroup_environment(); +}
--
2.43.0