linux-kernel - [PATCH v2 2/5] mm/memory-failure: fix race in counting num_poisoned

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Date:	Fri, 31 Jul 2015 06:46:13 +0000
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Andi Kleen <andi@...stfloor.org>, Dean Nelson <dnelson@...hat.com>,
	"Tony Luck" <tony.luck@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	"Hugh Dickins" <hughd@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Naoya Horiguchi" <nao.horiguchi@...il.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: [PATCH v2 2/5] mm/memory-failure: fix race in counting
 num_poisoned_pages

When memory_failure() is called on a page which are just freed after page
migration from soft offlining, the counter num_poisoned_pages is raised twice.
So let's fix it with using TestSetPageHWPoison.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
 mm/memory-failure.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git v4.2-rc4.orig/mm/memory-failure.c v4.2-rc4/mm/memory-failure.c
index 04d677048af7..f72d2fad0b90 100644
--- v4.2-rc4.orig/mm/memory-failure.c
+++ v4.2-rc4/mm/memory-failure.c
@@ -1671,8 +1671,8 @@ static int __soft_offline_page(struct page *page, int flags)
 			if (ret > 0)
 				ret = -EIO;
 		} else {
-			SetPageHWPoison(page);
-			atomic_long_inc(&num_poisoned_pages);
+			if (!TestSetPageHWPoison(page))
+				atomic_long_inc(&num_poisoned_pages);
 		}
 	} else {
 		pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
-- 
2.4.3
--
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