linux-kernel - Re: [PATCH v3 4/4] memory-hotplug: fix pages missed by race rather than failng

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Message-ID: <50494473.8030008@jp.fujitsu.com>
Date:	Fri, 07 Sep 2012 09:48:51 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Xishi Qiu <qiuxishi@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>
Subject: Re: [PATCH v3 4/4] memory-hotplug: fix pages missed by race rather
 than failng

(2012/09/07 9:39), Minchan Kim wrote:
> If race between allocation and isolation in memory-hotplug offline
> happens, some pages could be in MIGRATE_MOVABLE of free_list although
> the pageblock's migratetype of the page is MIGRATE_ISOLATE.
> 
> The race could be detected by get_freepage_migratetype
> in __test_page_isolated_in_pageblock. If it is detected, now EBUSY
> gets bubbled all the way up and the hotplug operations fails.
> 
> But better idea is instead of returning and failing memory-hotremove,
> move the free page to the correct list at the time it is detected.
> It could enhance memory-hotremove operation success ratio although
> the race is really rare.
> 
> Suggested-by: Mel Gorman <mgorman@...e.de>
> Signed-off-by: Minchan Kim <minchan@...nel.org>

Sounds reasonable. Thank you very much !

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


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