linux-kernel - Re: [PATCH AUTOSEL 6.14 20/54] mptcp: move the whole rx path under msk socket lock protection

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Message-ID: <Z_xTAoFA8RskUjCz@lappy>
Date: Sun, 13 Apr 2025 20:12:50 -0400
From: Sasha Levin <sashal@...nel.org>
To: Matthieu Baerts <matttbe@...nel.org>
Cc: Mat Martineau <martineau@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net,
	edumazet@...gle.com, netdev@...r.kernel.org, mptcp@...ts.linux.dev,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 6.14 20/54] mptcp: move the whole rx path under
 msk socket lock protection

On Thu, Apr 10, 2025 at 01:05:11PM +0200, Matthieu Baerts wrote:
>Hi Sasha,
>
>Thank you for having suggested this patch.
>
>On 03/04/2025 21:01, Sasha Levin wrote:
>> From: Paolo Abeni <pabeni@...hat.com>
>>
>> [ Upstream commit bc68b0efa1bf923cef1294a631d8e7416c7e06e4 ]
>>
>> After commit c2e6048fa1cf ("mptcp: fix race in release_cb") we can
>> move the whole MPTCP rx path under the socket lock leveraging the
>> release_cb.
>>
>> We can drop a bunch of spin_lock pairs in the receive functions, use
>> a single receive queue and invoke __mptcp_move_skbs only when subflows
>> ask for it.
>>
>> This will allow more cleanup in the next patch.
>>
>> Some changes are worth specific mention:
>>
>> The msk rcvbuf update now always happens under both the msk and the
>> subflow socket lock: we can drop a bunch of ONCE annotation and
>> consolidate the checks.
>>
>> When the skbs move is delayed at msk release callback time, even the
>> msk rcvbuf update is delayed; additionally take care of such action in
>> __mptcp_move_skbs().
>>
>> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
>> Reviewed-by: Mat Martineau <martineau@...nel.org>
>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
>> Link: https://patch.msgid.link/20250218-net-next-mptcp-rx-path-refactor-v1-3-4a47d90d7998@kernel.org
>> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>
>With Mat, we are unsure why this patch has been selected to be
>backported up to v6.6. An AUTOSEL patch has been sent for v6.6, v6.12,
>v6.13 and v6.14. We think it would be better not to backport this patch:
>this is linked to a new feature, and it changes the way the MPTCP socket
>locks are handled.
>
>Could it then please be possible not to queue this patch to the stable
>queues?

I'll drop it, thanks!

-- 
Thanks,
Sasha