linux-kernel - Re: [PATCH] net/udp_offload: Drop unnecessary continue

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Message-ID: <1407941291.6804.7.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 13 Aug 2014 07:48:11 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Himangi Saraogi <himangi774@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH] net/udp_offload: Drop unnecessary continue

On Wed, 2014-08-13 at 14:46 +0530, Himangi Saraogi wrote:
> Continue is not needed at the bottom of a loop.
> 
> The Coccinelle semantic patch implementing this change is:
> 
> @@
> @@
> 
> for (...;...;...) {
>   ...
>   if (...) {
>     ...
> -   continue;
>   }
> }
> 
> Signed-off-by: Himangi Saraogi <himangi774@...il.com>
> Acked-by: Julia Lawall <julia.lawall@...6.fr>
> ---
>  net/ipv4/udp_offload.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 59035bc..62d5b9b 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -269,10 +269,8 @@ unflush:
>  			continue;
>  
>  		uh2 = (struct udphdr   *)(p->data + off);
> -		if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
> +		if ((*(u32 *)&uh->source != *(u32 *)&uh2->source))
>  			NAPI_GRO_CB(p)->same_flow = 0;
> -			continue;
> -		}
>  	}
>  
>  	skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */


Please do not do that.

If we add another check later, we'll miss that the 'continue;' needs to
be put back.

GRO stack is quite difficult to maintain, I prefer we keep this as is
for consistency and code readability.

Every time we clear same_flow, we use the "continue;" construct.

 if (...) {
     NAPI_GRO_CB(p)->same_flow = 0;
     continue;
 }

<here we can eventually add some other check>

Compiler generates the same code anyway.



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