linux-kernel - Re: [PATCH 1/6] memcg: replace unsigned long by u64 to avoid overflow

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Message-ID: <20120625044638.GB3894@kernel>
Date:	Mon, 25 Jun 2012 12:46:38 +0800
From:	Wanpeng Li <liwp.linux@...il.com>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Balbir Singh <bsingharora@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Minchan Kim <minchan@...nel.org>,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	Gavin Shan <shangw@...ux.vnet.ibm.com>,
	Wanpen Li <liwp.linux@...il.com>
Subject: Re: [PATCH 1/6] memcg: replace unsigned long by u64 to avoid overflow

On Mon, Jun 25, 2012 at 01:24:26PM +0900, Kamezawa Hiroyuki wrote:
>(2012/06/23 18:26), Johannes Weiner wrote:
>>On Sat, Jun 23, 2012 at 05:03:39PM +0800, Wanpeng Li wrote:
>>>On Sat, Jun 23, 2012 at 10:15:14AM +0200, Johannes Weiner wrote:
>>>>On Sat, Jun 23, 2012 at 02:15:34PM +0800, Wanpeng Li wrote:
>>>>>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.
>>>>
>>>>I wonder what 16 TB of memory must think running on a 32-bit kernel...
>>>>"What is this, an address space for ants?"
>>>
>>>Hi Johannes,
>>>
>>>You mean change all u64 in memcg to unsigned long? or something I
>>>miss....
>>
>>Not _all_ of them, we have some that count bytes.  But those counting
>>pages should probably be ulong, yes.
>>
>>I think Kame added the ones that you wanted to adjust the surroundings
>>for in particular, so let's ask him.  Kame?
>>
>
>I've been using 'unsigned long' for the number of pages and 'u64' for the number of
>bytes. I think it's enough and it should be. I don't have any reason to use u64 for
>the number of pages on 32bit archs.
>If 'bytes' are handled by 'unsigned long', please fix it.
>
>BTW, zone_page_state()::/include/linux/vmstat.h returns 'unsigned long'.
>If you want to change this in memcg, please change zone's ones first.

Thank you for your comments Kame! :-) I will do this in next version.
Is any suggestion about patches in this patchset.

Regards,
Wanpeng Li

>
>Thanks,
>-Kame
>
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