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SubjectRe: [PATCH] hwpoison: Fix race with changing page during offlining v2
On Mon, Jun 30, 2014 at 05:32:16PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> When a hwpoison page is locked it could change state
> due to parallel modifications. Check after the lock
> if the page is still the same compound page.
>
> [v2: Removed earlier non LRU check which should be already
> covered elsewhere]
>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>

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

Is it -stable matter?
Maybe 2.6.38+ can profit from this.

Thanks,
Naoya Horiguchi

> ---
> mm/memory-failure.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index cd8989c..99e5077 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1168,6 +1168,16 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
> lock_page(hpage);
>
> /*
> + * The page could have changed compound pages during the locking.
> + * If this happens just bail out.
> + */
> + if (compound_head(p) != hpage) {
> + action_result(pfn, "different compound page after locking", IGNORED);
> + res = -EBUSY;
> + goto out;
> + }
> +
> + /*
> * We use page flags to determine what action should be taken, but
> * the flags can be modified by the error containment action. One
> * example is an mlocked page, where PG_mlocked is cleared by
> --
> 1.9.3
>
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