Date: Wed, 27 Mar 2013 17:58:28 -0400
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mel@csn.ul.ie>, Hugh Dickins <hughd@google.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Andi Kleen <andi@firstfloor.org>, Hillf Danton <dhillf@gmail.com>,
        linux-kernel@vger.kernel.org
Message-ID: <1364421508-fjm1vfw0-mutt-n-horiguchi@ah.jp.nec.com>
In-Reply-To: <1364419759-a5hijyn0-mutt-n-horiguchi@ah.jp.nec.com>
References: <1363983835-20184-1-git-send-email-n-horiguchi@ah.jp.nec.com>
 <1363983835-20184-10-git-send-email-n-horiguchi@ah.jp.nec.com>
 <20130325150952.GA2154@dhcp22.suse.cz>
 <1364322204-ah777uqs-mutt-n-horiguchi@ah.jp.nec.com>
 <20130327141921.GJ16579@dhcp22.suse.cz>
 <1364419759-a5hijyn0-mutt-n-horiguchi@ah.jp.nec.com>
Subject: Re: [PATCH 09/10] memory-hotplug: enable memory hotplug to handle
 hugepage
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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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