mm: soft-offline: fix num_poisoned_pages counting on concurrent events

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-horiguchi@ah.jp.nec.com>
Acked-by: Dean Nelson <dnelson@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: <stable@vger.kernel.org>	[3.14+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 22e0f270e4f7..501820c815b3 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1777,12 +1777,12 @@ int soft_offline_page(struct page *page, int flags)
         } else if (ret == 0) { /* 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_migratetype_isolate(page, MIGRATE_MOVABLE);