Re: [PATCH bpf-next v2 1/2] selftests/bpf: Keep the bpffs of cgroup_hierarchical_stats private

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] bpf: unbalanced lifecycle in destroy_hierarchy() teardown
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commit be18155cbccd124da201337ba01f9571021f8d5c
Author: Qiliang Yuan <odys.yuan@gmail.com>

selftests/bpf: Keep the bpffs of cgroup_hierarchical_stats private

setup_hierarchy() mounts a bpffs on /sys/fs/bpf with setup_bpffs(), and
then sets up the cgroups with setup_cgroups(), which moves the test into
a private mount namespace. The patch sets up the cgroups first, so that
the bpffs is mounted in the private mount namespace.

> diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_hierarchical_stats.c b/tools/testing/selftests/bpf/prog_tests/cgroup_hierarchical_stats.c
> index 3bd27d2ea668c..ad19d6d41918a 100644
> --- a/tools/testing/selftests/bpf/prog_tests/cgroup_hierarchical_stats.c
> +++ b/tools/testing/selftests/bpf/prog_tests/cgroup_hierarchical_stats.c
> @@ -151,7 +151,7 @@ static void cleanup_cgroups(void)
>  /* Sets up cgroup hiearchary, returns 0 on success. */
>  static int setup_hierarchy(void)
>  {
> -	return setup_bpffs() || setup_cgroups();
> +	return setup_cgroups() || setup_bpffs();
>  }
>  
>  static void destroy_hierarchy(void)

[Severity: Low]
Does destroy_hierarchy() need to be updated to reverse the teardown order?

Because the setup order has been changed to initialize cgroups before bpffs,
the test is placed in a private mount namespace before mounting the BPF
filesystem. 

However, destroy_hierarchy() continues to execute teardown in FIFO order
(cleanup_cgroups() followed by cleanup_bpffs()) instead of LIFO order.

While cleanup_cgroups() does not fully destroy the namespace until process
exit (preventing immediate crashes during cleanup_bpffs()), should
cleanup_bpffs() be called before cleanup_cgroups() to properly mirror the
new initialization order?

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Sashiko AI review · https://sashiko.dev/#/patchset/20261009-selftests-bpf-cgroup-stats-bpffs-v2-0-f93a111da992@gmail.com?part=1