Re: [PATCH bpf-next v2 1/6] selftests/bpf: test_progs: add test__join_cgroup helper

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Stanislav Fomichev <sdf@google.com>
Cc: Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH bpf-next v2 1/6] selftests/bpf: test_progs: add test__join_cgroup helper
Date: Fri, 6 Sep 2019 23:29:49 +0100	[thread overview]
Message-ID: <CAEf4Bzb=0gJv148r+RARMOYHikvvrzXJ-o5jQ7F_WtSzhRF38w@mail.gmail.com> (raw)
In-Reply-To: <20190905152709.111193-2-sdf@google.com>

On Thu, Sep 5, 2019 at 7:40 PM Stanislav Fomichev <sdf@google.com> wrote:
>
> test__join_cgroup() combines the following operations that usually
> go hand in hand and returns cgroup fd:
>
>   * setup cgroup environment (make sure cgroupfs is mounted)
>   * mkdir cgroup
>   * join cgroup
>
> It also marks a test as a "cgroup cleanup needed" and removes cgroup
> state after the test is done.
>
> Signed-off-by: Stanislav Fomichev <sdf@google.com>
> ---

First of all, thanks a lot for all these improvements to test_progs
and converting existing tests to test_progs tests, it's great to see
this consolidation!

[...]

> @@ -17,6 +18,7 @@ struct prog_test_def {
>         int error_cnt;
>         int skip_cnt;
>         bool tested;
> +       bool need_cgroup_cleanup;
>
>         const char *subtest_name;
>         int subtest_num;
> @@ -122,6 +124,39 @@ void test__fail(void)
>         env.test->error_cnt++;
>  }
>
> +int test__join_cgroup(const char *path)

This doesn't seem to be testing-specific functionality, tbh. It's
certainly useful helper, but I don't think it warrants test__ prefix.

As for test->need_cgroup_cleanup field, this approach won't scale if
we need other types of custom/optional clean up after test ends.
Generic test framework code will need to know about every possible
custom setup to be able to cleanup/undo it.

I wonder if generalizing it to be able to add custom clean up code
(some test frameworks have "teardown" overrides for this) would be
cleaner and more maintainable solution.

Something like:

typedef void (* test_teardown_fn)(struct test *test, void *ctx);

/* somewhere at the beginning of test: */
test__schedule_teardown(test_teardown_fn cb, void *ctx);

[...]

> +
> +               if (test->need_cgroup_cleanup)
> +                       cleanup_cgroup_environment();

Then in generic framework we'll just process a list of callbacks and
call each one with stored ctx per each callback (in case we need some
custom data to be stored, of course).

Thoughts?

[...]