linux-kernel - Re: [PATCH 1/5 v2] memcg: replace unsigned long by u64 to avoid overflow

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Message-ID: <20120625075215.GW27816@cmpxchg.org>
Date:	Mon, 25 Jun 2012 09:52:15 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Wanpeng Li <liwp.linux@...il.com>
Cc:	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <bsingharora@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mike Frysinger <vapier@...too.org>,
	Arun Sharma <asharma@...com>, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org
Subject: Re: [PATCH 1/5 v2] memcg: replace unsigned long by u64 to avoid
 overflow

On Mon, Jun 25, 2012 at 02:04:20PM +0800, Wanpeng Li wrote:
> Changlog:
> 
> V2 -> V1:
> * fix zone_page_state()::/include/linux/vmstat.h returns 'unsigned long'
> 
> From: Wanpeng Li <liwp@...ux.vnet.ibm.com>
> 
> Since the return value variable in mem_cgroup_zone_nr_lru_pages and
> mem_cgroup_node_nr_lru_pages functions are u64, so replace the return
> value of funtions by u64 to avoid overflow.
> 
> Signed-off-by: Wanpeng Li <liwp.linux@...il.com>
> ---
>  include/linux/vmstat.h |    2 +-
>  mm/memcontrol.c        |    5 ++---
>  2 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> index 65efb92..6a14291 100644
> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -106,7 +106,7 @@ static inline unsigned long global_page_state(enum zone_stat_item item)
>  	return x;
>  }
>  
> -static inline unsigned long zone_page_state(struct zone *zone,
> +static inline u64 zone_page_state(struct zone *zone,
>  					enum zone_stat_item item)
>  {
>  	long x = atomic_long_read(&zone->vm_stat[item]);

We established that there is no known reason to use ulong for page
counters and that IF YOU HAD ONE, you should obviously say so and then
do a wholesale conversion.  But I don't think you have one.

This patch makes absolutely no sense.
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