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Date: Sat, 8 Nov 2008 11:46:16 +0900 (JST)
Subject: Re: 2.6.28-rc3 mem_cgroup panic
From: "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>
To: "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Badari Pulavarty" <pbadari@us.ibm.com>,
       "Balbir Singh" <balbir@in.ibm.com>, "linux-mm" <linux-mm@kvack.org>,
       "linux-kernel" <linux-kernel@vger.kernel.org>
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KAMEZAWA Hiroyuki said:
> Badari Pulavarty said:
>> Hi Balbir,
>>
>> I was running memory remove/add tests in a continuous loop.
>> I get following panic in mem_cgroup migration code.
>>
>> Is this a known issue ?
>>
> No, this is new one. We don't see panic in cpuset based migration..so..
> Maybe related to page_cgroup allocation/free code in memory hotplug
> notifier.
>
> Thank you for report. I'll try this.
>
Hmm...at quick look...

online/offline page_cgroup's calculation for "start" is buggy..

-start = start_pfn & (PAGES_PER_SECTION - 1);
+start = start_pfn & ~(PAGES_PER_SECTION - 1);

I'm sorry I can't write patch today.

Regards,
-Kame

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