From: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 602498f9aa43d4951eece3fd6ad95a6d0a78d537 upstream.

If multiple soft offline events hit one free page/hugepage concurrently,
soft_offline_page() can handle the free page/hugepage multiple times,
which makes num_poisoned_pages counter increased more than once.  This
patch fixes this wrong counting by checking TestSetPageHWPoison for normal
papes and by checking the return value of dequeue_hwpoisoned_huge_page()
for hugepages.

Signed-off-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
Acked-by: Dean Nelson <dnel...@redhat.com>
Cc: Andi Kleen <a...@firstfloor.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Jiri Slaby <jsl...@suse.cz>
---
 mm/memory-failure.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 2e94ad1133af..5785b59620ef 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1718,12 +1718,12 @@ int soft_offline_page(struct page *page, int flags)
        } else { /* for free pages */
                if (PageHuge(page)) {
                        set_page_hwpoison_huge_page(hpage);
-                       dequeue_hwpoisoned_huge_page(hpage);
-                       atomic_long_add(1 << compound_order(hpage),
+                       if (!dequeue_hwpoisoned_huge_page(hpage))
+                               atomic_long_add(1 << compound_order(hpage),
                                        &num_poisoned_pages);
                } else {
-                       SetPageHWPoison(page);
-                       atomic_long_inc(&num_poisoned_pages);
+                       if (!TestSetPageHWPoison(page))
+                               atomic_long_inc(&num_poisoned_pages);
                }
        }
 unset:
-- 
2.3.7

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