linux-kernel - Re: [patch 1/2] mm, migration: add destination page freeing callback

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Date:	Thu, 1 May 2014 14:02:32 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	vbabka@...e.cz, iamjoonsoo.kim@....com, gthelen@...gle.com,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [patch 1/2] mm, migration: add destination page freeing
 callback

On Thu, 1 May 2014, Naoya Horiguchi wrote:

> Looks good to me.
> Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> 

Thanks!

> I have one comment below ...
> 
> [snip]
> 
> > @@ -1056,20 +1059,30 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
> >  	if (!page_mapped(hpage))
> >  		rc = move_to_new_page(new_hpage, hpage, 1, mode);
> >  
> > -	if (rc)
> > +	if (rc != MIGRATEPAGE_SUCCESS)
> >  		remove_migration_ptes(hpage, hpage);
> >  
> >  	if (anon_vma)
> >  		put_anon_vma(anon_vma);
> >  
> > -	if (!rc)
> > +	if (rc == MIGRATEPAGE_SUCCESS)
> >  		hugetlb_cgroup_migrate(hpage, new_hpage);
> >  
> >  	unlock_page(hpage);
> >  out:
> >  	if (rc != -EAGAIN)
> >  		putback_active_hugepage(hpage);
> > -	put_page(new_hpage);
> > +
> > +	/*
> > +	 * If migration was not successful and there's a freeing callback, use
> > +	 * it.  Otherwise, put_page() will drop the reference grabbed during
> > +	 * isolation.
> > +	 */
> 
> This comment is true both for normal page and huge page, and people more likely
> to see unmap_and_move() at first, so this had better be (also) in unmap_and_move().
> 

Ok!
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