linux-kernel - Re: [PATCH 3/3] HWPOISON, hugetlbfs: fix RSS-counter warning

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Message-Id: <20121206181024.f8a77240.akpm@linux-foundation.org>
Date:	Thu, 6 Dec 2012 18:10:24 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Tony Luck <tony.luck@...el.com>, Andi Kleen <andi.kleen@...el.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 3/3] HWPOISON, hugetlbfs: fix RSS-counter warning

On Thu,  6 Dec 2012 20:22:42 -0500 Naoya Horiguchi <n-horiguchi@...jp.nec.com> wrote:

> > --- a/mm/rmap.c~hwpoison-hugetlbfs-fix-rss-counter-warning-fix
> > +++ a/mm/rmap.c
> > @@ -1249,14 +1249,14 @@ int try_to_unmap_one(struct page *page, 
> >  	update_hiwater_rss(mm);
> >  
> >  	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
> > -		if (PageHuge(page))
> > -			;
> > -		else if (PageAnon(page))
> > -			dec_mm_counter(mm, MM_ANONPAGES);
> > -		else
> > -			dec_mm_counter(mm, MM_FILEPAGES);
> > -		set_pte_at(mm, address, pte,
> > -				swp_entry_to_pte(make_hwpoison_entry(page)));
> > +		if (!PageHuge(page)) {
> > +			if (PageAnon(page))
> > +				dec_mm_counter(mm, MM_ANONPAGES);
> > +			else
> > +				dec_mm_counter(mm, MM_FILEPAGES);
> > +			set_pte_at(mm, address, pte,
> > +				   swp_entry_to_pte(make_hwpoison_entry(page)));
> > +		}
> 
> This set_pte_at() should come outside the if-block, or error containment
> does not work.

Doh.  C is really hard!

--- a/mm/rmap.c~hwpoison-hugetlbfs-fix-rss-counter-warning-fix-fix
+++ a/mm/rmap.c
@@ -1254,9 +1254,9 @@ int try_to_unmap_one(struct page *page, 
 				dec_mm_counter(mm, MM_ANONPAGES);
 			else
 				dec_mm_counter(mm, MM_FILEPAGES);
-			set_pte_at(mm, address, pte,
-				   swp_entry_to_pte(make_hwpoison_entry(page)));
 		}
+		set_pte_at(mm, address, pte,
+			   swp_entry_to_pte(make_hwpoison_entry(page)));
 	} else if (PageAnon(page)) {
 		swp_entry_t entry = { .val = page_private(page) };
 
_

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