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    Subject[PATCH 3.19.y-ckt 69/92] mm: soft-offline: fix num_poisoned_pages counting on concurrent events
    Date
    3.19.8-ckt1 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

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

    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-horiguchi@ah.jp.nec.com>
    Acked-by: Dean Nelson <dnelson@redhat.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    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 5e71ba3..dc29bec 100644
    --- a/mm/memory-failure.c
    +++ b/mm/memory-failure.c
    @@ -1728,12 +1728,12 @@ 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);
    --
    1.9.1


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