netdev - Re: [PATCH] net: fix bogus cast in skb_pagelen() and use unsigned variables

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Date:   Sat, 19 Nov 2016 22:12:15 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     adobriyan@...il.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH] net: fix bogus cast in skb_pagelen() and use unsigned
 variables

From: Alexey Dobriyan <adobriyan@...il.com>
Date: Sat, 19 Nov 2016 04:08:08 +0300

> 1) cast to "int" is unnecessary:
>    u8 will be promoted to int before decrementing,
>    small positive numbers fit into "int", so their values won't be changed
>    during promotion.
> 
>    Once everything is int including loop counters, signedness doesn't
>    matter: 32-bit operations will stay 32-bit operations.
> 
>    But! Someone tried to make this loop smart by making everything of
>    the same type apparently in an attempt to optimise it.
>    Do the optimization, just differently.
>    Do the cast where it matters. :^)
> 
> 2) frag size is unsigned entity and sum of fragments sizes is also
>    unsigned.
> 
> Make everything unsigned, leave no MOVSX instruction behind.
 ...
> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>

Applied to net-next.