Re: [RESEND PATCH bpf-next v9 5/5] selftests/bpf: add a selftest for cgroup hierarchical stats collection

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Wed, Aug 24, 2022 at 4:31 PM Hao Luo <haoluo@google.com> wrote:
> +
> +       for (i = 0; i < N_CGROUPS; i++) {
> +               fd = create_and_get_cgroup(cgroups[i].path);
> +               if (!ASSERT_GE(fd, 0, "create_and_get_cgroup"))
> +                       return fd;
> +
> +               cgroups[i].fd = fd;
> +               cgroups[i].id = get_cgroup_id(cgroups[i].path);
> +
> +               /*
> +                * Enable memcg controller for the entire hierarchy.
> +                * Note that stats are collected for all cgroups in a hierarchy
> +                * with memcg enabled anyway, but are only exposed for cgroups
> +                * that have memcg enabled.
> +                */
> +               if (i < N_NON_LEAF_CGROUPS) {
> +                       err = enable_controllers(cgroups[i].path, "memory");
> +                       if (!ASSERT_OK(err, "enable_controllers"))
> +                               return err;
> +               }
> +       }

It passes BPF CI, but fails in my setup with:

# ./test_progs -t cgroup_hier -vv
bpf_testmod.ko is already unloaded.
Loading bpf_testmod.ko...
Successfully loaded bpf_testmod.ko.
setup_bpffs:PASS:mount 0 nsec
setup_cgroups:PASS:setup_cgroup_environment 0 nsec
setup_cgroups:PASS:get_root_cgroup 0 nsec
setup_cgroups:PASS:create_and_get_cgroup 0 nsec
(cgroup_helpers.c:92: errno: No such file or directory) Enabling
controller memory:
/mnt/cgroup-test-work-dir6526//test/cgroup.subtree_control
setup_cgroups:FAIL:enable_controllers unexpected error: 1 (errno 2)
cleanup_bpffs:FAIL:rmdir /sys/fs/bpf/vmscan/ unexpected error: -1 (errno 2)
#36      cgroup_hierarchical_stats:FAIL
Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED

How do I debug it?