linux-kernel - Re: [PATCH] mptcp: Remove redundant assignment to remaining

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Date:   Tue, 15 Jun 2021 16:52:25 -0700 (PDT)
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
cc:     matthieu.baerts@...sares.net, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, mptcp@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mptcp: Remove redundant assignment to remaining

On Tue, 15 Jun 2021, Jiapeng Chong wrote:

> Variable remaining is assigned, but this value is never read as it is
> not used later on, hence it is a redundant assignment and can be
> removed.
>
> Clean up the following clang-analyzer warning:
>
> net/mptcp/options.c:779:3: warning: Value stored to 'remaining' is never
> read [clang-analyzer-deadcode.DeadStores].
>
> net/mptcp/options.c:547:3: warning: Value stored to 'remaining' is never
> read [clang-analyzer-deadcode.DeadStores].
>
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
> net/mptcp/options.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> index 9b263f2..f99272f 100644
> --- a/net/mptcp/options.c
> +++ b/net/mptcp/options.c
> @@ -544,7 +544,6 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
>
> 		map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
>
> -		remaining -= map_size;

Hi Jiapeng, thank you for your MPTCP patch!

This change in mptcp_established_options_dss() removes the only reference 
to 'remaining' in that function, so the variable should also be removed 
from the function parameters. It also appears to be unused in 
mptcp_established_options_mp().

I'd like to handle this patch through the MPTCP tree so we can manage 
conflicts with other in-progress patches. This patch does apply to 
net-next cleanly but not our subsystem branch. You can find our git repo 
at https://github.com/multipath-tcp/mptcp_net-next, and develop patches 
using the 'export' branch. If you email a v2 patch to 
mptcp@...ts.linux.dev (no need to cc other lists), Matthieu and I can make 
sure it is integrated in the MPTCP repository and handle sending it to 
netdev along with other patches from the MPTCP community.

> 		dss_size = map_size;
> 		if (mpext)
> 			opts->ext_copy = *mpext;
> @@ -776,7 +775,6 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
>
> 	if (mptcp_established_options_mp_prio(sk, &opt_size, remaining, opts)) {
> 		*size += opt_size;
> -		remaining -= opt_size;
> 		ret = true;
> 	}
>
> -- 
> 1.8.3.1

Best regards,

--
Mat Martineau
Intel