linux-kernel - Re: [PATCH net] net/smc: avoid overwriting when adjusting sock bufsizes

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Date: Tue, 04 Jun 2024 16:04:59 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Wen Gu <guwen@...ux.alibaba.com>, gbayer@...ux.ibm.com, 
 wenjia@...ux.ibm.com, jaka@...ux.ibm.com, davem@...emloft.net,
 edumazet@...gle.com,  kuba@...nel.org
Cc: alibuda@...ux.alibaba.com, tonylu@...ux.alibaba.com, 
 linux-s390@...r.kernel.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net/smc: avoid overwriting when adjusting sock
 bufsizes

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 <guwen@...ux.alibaba.com>
> ---
> FYI,
> The detailed motivation and testing can be found in the link above.

My understanding is that there is an open question here if this is the
expected and desired behavior.

@Wenjia, @Jan: could you please have a look?

Thanks!

Paolo