linux-kernel - Re: [PATCH 02/24] migrate: page could be locked by hwpoison, dont BUG()

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Message-ID: <20091203013433.GA8520@localhost>
Date:	Thu, 3 Dec 2009 09:34:33 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 02/24] migrate: page could be locked by hwpoison, dont
	BUG()

On Wed, Dec 02, 2009 at 10:50:10PM +0800, Christoph Lameter wrote:
> On Wed, 2 Dec 2009, Wu Fengguang wrote:
> 
> >  mm/migrate.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > --- linux-mm.orig/mm/migrate.c	2009-11-02 10:18:45.000000000 +0800
> > +++ linux-mm/mm/migrate.c	2009-11-02 10:26:16.000000000 +0800
> > @@ -556,7 +556,7 @@ static int move_to_new_page(struct page
> >  	 * holding a reference to the new page at this point.
> >  	 */
> >  	if (!trylock_page(newpage))
> > -		BUG();
> > +		return -EAGAIN;		/* got by hwpoison */
> >
> >  	/* Prepare mapping for the new page.*/
> >  	newpage->index = page->index;
> 
> The error handling code in umap_and_move() assumes that the page is
> locked upon return from move_to_new_page() even if it failed.
> 
> If you return EAGAIN then it may try to unlock a page that is not
> locked.

Ah yes, thanks!  We could fix it with more changes, however it seems
better to just drop this patch.

Thanks,
Fengguang
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