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    Subject[PATCH] [6/31] HWPOISON: avoid grabbing the page count multiple times during madvise injection
    Date

    From: Wu Fengguang <fengguang.wu@intel.com>

    If page is double referenced in madvise_hwpoison() and __memory_failure(),
    remove_mapping() will fail because it expects page_count=2. Fix it by
    not grabbing extra page count in __memory_failure().

    Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    Signed-off-by: Andi Kleen <ak@linux.intel.com>

    ---
    mm/madvise.c | 1 -
    mm/memory-failure.c | 8 ++++----
    2 files changed, 4 insertions(+), 5 deletions(-)

    Index: linux/mm/madvise.c
    ===================================================================
    --- linux.orig/mm/madvise.c
    +++ linux/mm/madvise.c
    @@ -238,7 +238,6 @@ static int madvise_hwpoison(unsigned lon
    page_to_pfn(p), start);
    /* Ignore return value for now */
    __memory_failure(page_to_pfn(p), 0, 1);
    - put_page(p);
    }
    return ret;
    }
    Index: linux/mm/memory-failure.c
    ===================================================================
    --- linux.orig/mm/memory-failure.c
    +++ linux/mm/memory-failure.c
    @@ -629,7 +629,7 @@ static void action_result(unsigned long
    }

    static int page_action(struct page_state *ps, struct page *p,
    - unsigned long pfn, int ref)
    + unsigned long pfn)
    {
    int result;
    int count;
    @@ -637,7 +637,7 @@ static int page_action(struct page_state
    result = ps->action(p, pfn);
    action_result(pfn, ps->msg, result);

    - count = page_count(p) - 1 - ref;
    + count = page_count(p) - 1;
    if (count != 0)
    printk(KERN_ERR
    "MCE %#lx: %s page still referenced by %d users\n",
    @@ -775,7 +775,7 @@ int __memory_failure(unsigned long pfn,
    * In fact it's dangerous to directly bump up page count from 0,
    * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
    */
    - if (!get_page_unless_zero(compound_head(p))) {
    + if (!ref && !get_page_unless_zero(compound_head(p))) {
    action_result(pfn, "free or high order kernel", IGNORED);
    return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
    }
    @@ -823,7 +823,7 @@ int __memory_failure(unsigned long pfn,
    res = -EBUSY;
    for (ps = error_states;; ps++) {
    if (((p->flags | lru_flag)& ps->mask) == ps->res) {
    - res = page_action(ps, p, pfn, ref);
    + res = page_action(ps, p, pfn);
    break;
    }
    }

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