linux-kernel - Re: [PATCH V2] MCE: fix an error of mce_bad

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Message-ID: <50C6CAC3.1090809@huawei.com>
Date:	Tue, 11 Dec 2012 13:55:15 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Simon Jeons <simon.jeons@...il.com>
CC:	Andi Kleen <andi@...stfloor.org>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	WuJianguo <wujianguo@...wei.com>,
	Liujiang <jiang.liu@...wei.com>, <Vyacheslav.Dubeyko@...wei.com>,
	Borislav Petkov <bp@...en8.de>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, <wency@...fujitsu.com>
Subject: Re: [PATCH V2] MCE: fix an error of mce_bad_pages statistics

On 2012/12/11 11:48, Simon Jeons wrote:

> On Tue, 2012-12-11 at 04:19 +0100, Andi Kleen wrote:
>> On Mon, Dec 10, 2012 at 09:13:11PM -0600, Simon Jeons wrote:
>>> On Tue, 2012-12-11 at 04:01 +0100, Andi Kleen wrote:
>>>>> Oh, it will be putback to lru list during migration. So does your "some
>>>>> time" mean before call check_new_page?
>>>>
>>>> Yes until the next check_new_page() whenever that is. If the migration
>>>> works it will be earlier, otherwise later.
>>>
>>> But I can't figure out any page reclaim path check if the page is set
>>> PG_hwpoison, can poisoned pages be rclaimed?
>>
>> The only way to reclaim a page is to free and reallocate it.
> 
> Then why there doesn't have check in reclaim path to avoid relcaim
> poisoned page?
> 
> 			-Simon

Hi Simon,

If the page is free, it will be set PG_hwpoison, and soft_offline_page() is done.
When the page is alocated later, check_new_page() will find the poisoned page and
isolate the whole buddy block(just drop the block).

If the page is not free, soft_offline_page() try to free it first, if this is
failed, it will migrate the page, but the page is still in LRU list after migration,
migrate_pages()
	unmap_and_move()
		if (rc != -EAGAIN) {
			...
			putback_lru_page(page);
		}
We can use lru_add_drain_all() to drain lru pagevec, at last free_hot_cold_page()
will be called, and free_pages_prepare() check the poisoned pages.
free_pages_prepare()
	free_pages_check()
		bad_page()

Is this right, Andi?

Thanks
Xishi Qiu

>>
>> -Andi
> 
> 
> 
> 



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