linux-kernel - [PATCH] HWPOSION, hugetlb: lock_page/unlock_page does not match for handling a free hugepage

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Message-ID: <1399688409.28090.0.camel@cyc>
Date:	Sat, 10 May 2014 10:20:09 +0800
From:	Chen Yucong <slaoub@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH] HWPOSION, hugetlb: lock_page/unlock_page does not match for
 handling a free hugepage

For handling a free hugepage in memory failure, the race will happen if
another thread hwpoisoned this hugepage concurrently. So we need to
check PageHWPoison instead of !PageHWPoison.

If hwpoison_filter(p) returns true or a race happens, then we need to
unlock_page(hpage).

Signed-off-by: Chen Yucong <slaoub@...il.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
mm/memory-failure.c |   15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 35ef28a..dbf8922 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1081,15 +1081,16 @@ int memory_failure(unsigned long pfn, int
trapno, int flags)
 			return 0;
 		} else if (PageHuge(hpage)) {
 			/*
-			 * Check "just unpoisoned", "filter hit", and
-			 * "race with other subpage."
+			 * Check "filter hit" and "race with other subpage."
 			 */
 			lock_page(hpage);
-			if (!PageHWPoison(hpage)
-			    || (hwpoison_filter(p) && TestClearPageHWPoison(p))
-			    || (p != hpage && TestSetPageHWPoison(hpage))) {
-				atomic_long_sub(nr_pages, &num_poisoned_pages);
-				return 0;
+			if (PageHWPoison(hpage)) {
+				if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
+				    || (p != hpage && TestSetPageHWPoison(hpage))) {
+					atomic_long_sub(nr_pages, &num_poisoned_pages);
+					unlock_page(hpage);
+					return 0;
+				}
 			}
 			set_page_hwpoison_huge_page(hpage);
 			res = dequeue_hwpoisoned_huge_page(hpage);
-- 
1.7.10.4




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