From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-100.freemail.mail.aliyun.com (out30-100.freemail.mail.aliyun.com [115.124.30.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ECEFB225D9; Wed, 5 Jun 2024 06:01:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.100 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717567293; cv=none; b=fGUxUmBNJ4gO20gPi9HdUMYhHkSJ4CbPICsuHH1R0FXNL713X0n8Aiwp5VKw21qybhT4G6ZfrS/tNyb4UB/b9C/uqJlp9+8q7YXN5pEIqAupfRX0fmV2wDjBFjJI1+stXP4tRG6b9ApGvy+MmU4dVdn4/htfAr8rIm0L/3fsB1g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717567293; c=relaxed/simple; bh=kspRoPiqT+60w/910CphqXYKi5/A7+b0R+YvgoUpxZc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DLXKgmW/eslF6jbeLaWu8Q/rH+MK7sFMZoXhbyvVajyw5IU7/QpOEm6ukI0uQ9d+gbTu6kfpOQocuUG5svhdDcYguQclHCnDS2K9AZC1rNwtbvWbMO2axYS77/5zK0TAh4w13CFLTOqm4vXOwHafP+g/m36ZJbfb1pn9xwgEvRQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=St/YVqDJ; arc=none smtp.client-ip=115.124.30.100 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="St/YVqDJ" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1717567282; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=7770HT+DXXn2uXZuUaw8VKFeHVqNBA2X1DYZ7hOedW8=; b=St/YVqDJe1lhFH2rmcg3mHt8YDInlq7ToOb77QOwpq3qha8rbSTPWt1yytlsMaWF//NmIVJcgVUe3Wdk1BrUdyiNxCFeW3JgV5nq9brwnbwDto8FsIxN6JoqLJHaMSY7gfRQkK8CvtKGSo61y9FCYJcnb4wensfOsqMfprcF8x8= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037067110;MF=guwen@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0W7t4AJs_1717567280; Received: from 30.221.129.197(mailfrom:guwen@linux.alibaba.com fp:SMTPD_---0W7t4AJs_1717567280) by smtp.aliyun-inc.com; Wed, 05 Jun 2024 14:01:21 +0800 Message-ID: <1884a3ff-1a1a-419c-b474-4d37bf760a77@linux.alibaba.com> Date: Wed, 5 Jun 2024 14:01:20 +0800 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] net/smc: avoid overwriting when adjusting sock bufsizes To: Gerd Bayer , wenjia@linux.ibm.com, jaka@linux.ibm.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: alibuda@linux.alibaba.com, tonylu@linux.alibaba.com, linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240531085417.43104-1-guwen@linux.alibaba.com> From: Wen Gu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024/6/5 00:16, Gerd Bayer wrote: > Hi Wen Gu, > > sorry for the late reply, I'm just catching up after a bit of a > vacation. No worries at all, I hope you had a great vacation! > > On Fri, 2024-05-31 at 16:54 +0800, Wen Gu wrote: >> When copying smc settings to clcsock, avoid setting clcsock's >> sk_sndbuf to sysctl_tcp_wmem[1], since this may overwrite the value >> set by tcp_sndbuf_expand() in TCP connection establishment. >> >> And the other setting sk_{snd|rcv}buf to sysctl value in >> smc_adjust_sock_bufsizes() can also be omitted since the >> initialization of smc sock and clcsock has set sk_{snd|rcv}buf to >> smc.sysctl_{w|r}mem or ipv4_sysctl_tcp_{w|r}mem[1]. >> >> Fixes: 30c3c4a4497c ("net/smc: Use correct buffer sizes when >> switching between TCP and SMC") >> Link: >> https://lore.kernel.org/r/5eaf3858-e7fd-4db8-83e8-3d7a3e0e9ae2@linux.alibaba.com >> Signed-off-by: Wen Gu >> --- >> FYI, >> The detailed motivation and testing can be found in the link above. >> --- <...> > > As Wenjia already said, we've discussed this a bit. > As I remember, I've added the sections to copy over the sysctl values > as a "safety measure" when moving between smc/clc sockets - but had the > wrong assumption in mind that e.g. in a fall-back a new TCP handshake > would be done. Apparently, we didn't test the buffer size behavior in > these scenarios enough to notice the "weird" behavior. > > So we reviewed your initial report of the oddity per your message in > the link above, too. > > We fully agree that if no connection at the SMC level could be > established, you should expect the socket buffersizes be used that had > been established for the TCP connection - regardless if the fallback is > due to the server or the client. > > So feel free to add my > Reviewed-by: Gerd Bayer , too. > Hi, Gerd and Wenjia. Thanks a lot for your confirmation. And as for the last question in the initial report (link above), that why the server does not call smc_copy_sock_settings_to_clc() like the client when fallback happens, I guess it is because at the time that server fallback, the new_smc sock has not been accepted, so there will be no user's sock settings that needs to be copied to clcsock. Thanks! > Thanks, > Gerd