Patch "hwpoison, hugetlb: lock_page/unlock_page does not match for handling a free hugepage" has been added to the 3.4-stable tree

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This is a note to let you know that I've just added the patch titled

    hwpoison, hugetlb: lock_page/unlock_page does not match for handling a free hugepage

to the 3.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     hwpoison-hugetlb-lock_page-unlock_page-does-not-match-for-handling-a-free-hugepage.patch
and it can be found in the queue-3.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From b985194c8c0a130ed155b71662e39f7eaea4876f Mon Sep 17 00:00:00 2001
From: Chen Yucong <slaoub@xxxxxxxxx>
Date: Thu, 22 May 2014 11:54:15 -0700
Subject: hwpoison, hugetlb: lock_page/unlock_page does not match for handling a free hugepage

From: Chen Yucong <slaoub@xxxxxxxxx>

commit b985194c8c0a130ed155b71662e39f7eaea4876f upstream.

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@xxxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Tested-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/memory-failure.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1061,15 +1061,16 @@ int memory_failure(unsigned long pfn, in
 			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, &mce_bad_pages);
-				return 0;
+			if (PageHWPoison(hpage)) {
+				if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
+				    || (p != hpage && TestSetPageHWPoison(hpage))) {
+					atomic_long_sub(nr_pages, &mce_bad_pages);
+					unlock_page(hpage);
+					return 0;
+				}
 			}
 			set_page_hwpoison_huge_page(hpage);
 			res = dequeue_hwpoisoned_huge_page(hpage);


Patches currently in stable-queue which might be from slaoub@xxxxxxxxx are

queue-3.4/hwpoison-hugetlb-lock_page-unlock_page-does-not-match-for-handling-a-free-hugepage.patch
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