linux-kernel - Re: [PATCH] [6/16] HWPOISON: Add various poison checks in mm/memory.c

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Date:	Tue, 9 Jun 2009 20:21:31 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andi Kleen <andi@...stfloor.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] [6/16] HWPOISON: Add various poison checks in
	mm/memory.c

On Tue, Jun 09, 2009 at 06:25:04PM +0800, Nick Piggin wrote:
> On Wed, Jun 03, 2009 at 08:46:38PM +0200, Andi Kleen wrote:
> > 
> > Bail out early when hardware poisoned pages are found in page fault handling.
> > Since they are poisoned they should not be mapped freshly into processes,
> > because that would cause another (potentially deadly) machine check
> > 
> > This is generally handled in the same way as OOM, just a different
> > error code is returned to the architecture code.
> > 
> > Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> > 
> > ---
> >  mm/memory.c |    3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > Index: linux/mm/memory.c
> > ===================================================================
> > --- linux.orig/mm/memory.c	2009-06-03 19:36:23.000000000 +0200
> > +++ linux/mm/memory.c	2009-06-03 19:36:23.000000000 +0200
> > @@ -2797,6 +2797,9 @@
> >  	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
> >  		return ret;
> >  
> > +	if (unlikely(PageHWPoison(vmf.page)))
> > +		return VM_FAULT_HWPOISON;
> 
> Again, it would be nice if you just worry about this in your MCE
> handler and don't sprinkle things like this in fastpaths.

For this patch, I cannot imagine a clear usage case for it, and
proposed to remove it until there comes a case.

Thanks,
Fengguang

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