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Date: Fri, 19 Jul 2013 10:39:56 -0400
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: Hillf Danton <dhillf@gmail.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>, Hugh Dickins <hughd@google.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Andi Kleen <andi@firstfloor.org>, Michal Hocko <mhocko@suse.cz>,
        Rik van Riel <riel@redhat.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org,
        Naoya Horiguchi <nao.horiguchi@gmail.com>
Message-ID: <1374244796-ur27gtic-mutt-n-horiguchi@ah.jp.nec.com>
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Subject: Re: [PATCH 7/8] memory-hotplug: enable memory hotplug to handle
 hugepage
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On Fri, Jul 19, 2013 at 01:40:38PM +0800, Hillf Danton wrote:
> On Fri, Jul 19, 2013 at 5:34 AM, Naoya Horiguchi
> <n-horiguchi@ah.jp.nec.com> wrote:
> > @@ -518,9 +519,11 @@ static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
> >  {
> >         struct page *page;
> >
> > -       if (list_empty(&h->hugepage_freelists[nid]))
> > +       list_for_each_entry(page, &h->hugepage_freelists[nid], lru)
> > +               if (!is_migrate_isolate_page(page))
> > +                       break;
> > +       if (&h->hugepage_freelists[nid] == &page->lru)
> 
> For what is this check?

This check returns true unless a non-isolated free hugepage is found.
In "not found" case page points to h->hugepage_freelists, so without
this check successive code doesn't work fine.

Thanks,
Naoya

> >                 return NULL;
> > -       page = list_entry(h->hugepage_freelists[nid].next, struct page, lru);
> >         list_move(&page->lru, &h->hugepage_activelist);
> >         set_page_refcounted(page);
> >         h->free_huge_pages--;
>
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