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Date: Wed, 8 May 2024 09:36:13 +0200
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Subject: Re: [PATCH bpf-next 2/4] selftests/bpf: Add RUN_MPTCP_TEST macro
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To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: MPTCP Upstream <mptcp@lists.linux.dev>,
 Mat Martineau <martineau@kernel.org>, Geliang Tang <geliang@kernel.org>,
 Andrii Nakryiko <andrii@kernel.org>, Eduard Zingerman <eddyz87@gmail.com>,
 Mykola Lysenko <mykolal@fb.com>, Alexei Starovoitov <ast@kernel.org>,
 Daniel Borkmann <daniel@iogearbox.net>,
 Martin KaFai Lau <martin.lau@linux.dev>, Song Liu <song@kernel.org>,
 Yonghong Song <yonghong.song@linux.dev>,
 John Fastabend <john.fastabend@gmail.com>, KP Singh <kpsingh@kernel.org>,
 Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
 Jiri Olsa <jolsa@kernel.org>, Shuah Khan <shuah@kernel.org>,
 LKML <linux-kernel@vger.kernel.org>,
 Network Development <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
 "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org>,
 Geliang Tang <tanggeliang@kylinos.cn>
References: <20240507-upstream-bpf-next-20240506-mptcp-subflow-test-v1-0-e2bcbdf49857@kernel.org>
 <20240507-upstream-bpf-next-20240506-mptcp-subflow-test-v1-2-e2bcbdf49857@kernel.org>
 <CAADnVQJ5-APFxMeGsUDSWBsiAbhJGivs=fBUapgYEFNHgnEVeA@mail.gmail.com>
 <d28dec16-9029-42f5-b979-a0f11656a991@kernel.org>
 <CAADnVQJM73g9gTq3GxR-RMmpJPK3DGgzUTQiJXjz_B1G_4JAAw@mail.gmail.com>
From: Matthieu Baerts <matttbe@kernel.org>
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Organization: NGI0 Core
In-Reply-To: <CAADnVQJM73g9gTq3GxR-RMmpJPK3DGgzUTQiJXjz_B1G_4JAAw@mail.gmail.com>
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Hi Alexei,

Thank you for your reply!

On 07/05/2024 22:51, Alexei Starovoitov wrote:
> On Tue, May 7, 2024 at 9:02 AM Matthieu Baerts <matttbe@kernel.org> wrote:
>>
>> Hi Alexei,
>>
>> Thank you for the review!
>>
>> On 07/05/2024 16:44, Alexei Starovoitov wrote:
>>> On Tue, May 7, 2024 at 3:53 AM Matthieu Baerts (NGI0)
>>> <matttbe@kernel.org> wrote:
>>>>
>>>> From: Geliang Tang <tanggeliang@kylinos.cn>
>>>>
>>>> Each MPTCP subtest tests test__start_subtest(suffix), then invokes
>>>> test_suffix(). It makes sense to add a new macro RUN_MPTCP_TEST to
>>>> simpolify the code.
>>>>
>>>> Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
>>>> Reviewed-by: Mat Martineau <martineau@kernel.org>
>>>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
>>>> ---
>>>>  tools/testing/selftests/bpf/prog_tests/mptcp.c | 12 ++++++++----
>>>>  1 file changed, 8 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c
>>>> index baf976a7a1dd..9d1b255bb654 100644
>>>> --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c
>>>> +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c
>>>> @@ -347,10 +347,14 @@ static void test_mptcpify(void)
>>>>         close(cgroup_fd);
>>>>  }
>>>>
>>>> +#define RUN_MPTCP_TEST(suffix)                                 \
>>>> +do {                                                           \
>>>> +       if (test__start_subtest(#suffix))                       \
>>>> +               test_##suffix();                                \
>>>> +} while (0)
>>>
>>> Please no.
>>> Don't hide it behind macros.
>>
>> I understand, I'm personally not a big fan of hiding code being a macro
>> too. This one saves only one line. Geliang added a few more tests in our
>> tree [1], for a total of 9, so that's only saving 9 lines.
>>
>> Related to that, if you don't mind, Geliang also added another macro --
>> MPTCP_SCHED_TEST -- for tests that are currently only in our tree [2]
>> (not ready yet). We asked him to reduce the size of this macro to the
>> minimum. We accepted it because it removed quite a lot of similar code
>> with very small differences [3]. Do you think we should revert this
>> modification too?
> 
> Yeah. Pls don't hide such things in macros.
> Refactor into helper function in normal C.

Sure, we will revert that.

> But, what do you mean "in your tree" ?
> That's your development tree and you plan to send all that
> properly as patches to bpf-next someday?

Yes, correct, we have some WIP patches in MPTCP development tree where
we added a new bpf_struct_ops structure to implement new MPTCP packet
schedulers in BPF. This work was paused for a while because we had to
refine the packet scheduler API, but this task is now ongoing. Hopefully
we will be able to send patches to bpf-next this "soon".

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.