linux-kernel - Re: [PATCH 09/22] HWPOISON: Handle hardware poisoned pages in try_to

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Date:	Mon, 15 Jun 2009 23:26:12 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>,
	Mel Gorman <mel@....ul.ie>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andi Kleen <andi@...stfloor.org>,
	"riel@...hat.com" <riel@...hat.com>,
	"chris.mason@...cle.com" <chris.mason@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 09/22] HWPOISON: Handle hardware poisoned pages in
	try_to_unmap

On Mon, Jun 15, 2009 at 09:09:03PM +0800, Minchan Kim wrote:
> On Mon, Jun 15, 2009 at 11:45 AM, Wu Fengguang<fengguang.wu@...el.com> wrote:
> > From: Andi Kleen <ak@...ux.intel.com>
> >
> > When a page has the poison bit set replace the PTE with a poison entry.
> > This causes the right error handling to be done later when a process runs
> > into it.
> >
> > Also add a new flag to not do that (needed for the memory-failure handler
> > later)
> >
> > Reviewed-by: Wu Fengguang <fengguang.wu@...el.com>
> > Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> >
> > ---
> >  include/linux/rmap.h |    1 +
> >  mm/rmap.c            |    9 ++++++++-
> >  2 files changed, 9 insertions(+), 1 deletion(-)
> >
> > --- sound-2.6.orig/mm/rmap.c
> > +++ sound-2.6/mm/rmap.c
> > @@ -958,7 +958,14 @@ static int try_to_unmap_one(struct page
> >        /* Update high watermark before we lower rss */
> >        update_hiwater_rss(mm);
> >
> > -       if (PageAnon(page)) {
> > +       if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
> > +               if (PageAnon(page))
> > +                       dec_mm_counter(mm, anon_rss);
> > +               else if (!is_migration_entry(pte_to_swp_entry(*pte)))
> 
> Isn't it straightforward to use !is_hwpoison_entry ?

Good catch!  It looks like a redundant check: the
page_check_address() at the beginning of the function guarantees that 
!is_migration_entry() or !is_migration_entry() tests will all be TRUE.

So let's do this?

-               else if (!is_migration_entry(pte_to_swp_entry(*pte)))
+               else


Thanks,
Fengguang
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