linux-kernel - Re: [PATCH 09/10] memory-hotplug: enable memory hotplug to handle hugepage

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Date:	Wed, 27 Mar 2013 17:58:28 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Hillf Danton <dhillf@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/10] memory-hotplug: enable memory hotplug to handle
 hugepage

On Wed, Mar 27, 2013 at 05:29:19PM -0400, Naoya Horiguchi wrote:
...
> > If we made sure that all page on the hugepage_freelists have reference
> > 0 (which is now not the case and it is yet another source of confusion)
> > then the whole loop could be replaced by page_count check.
> 
> I think that free hugepages have refcount 0, but hwpoisoned hugepages
> have also refcount 0. But hwpoison can happen only on limited hardware
> and we consider them as exceptional, so replacing page_count check and
> checking PG_hwpoisoned flag looks more reasonable to me.

Sorry, my mistake. Hwpoisoned hugepages have refcount 1, so there's
no problem on using page_count check.

Naoya
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