linux-kernel - Re: [PATCH] hwpoison: Fix race with changing page during offlining v2

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Date:	Mon, 30 Jun 2014 21:21:46 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [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@...ux.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@...jp.nec.com>
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>

Acked-by: Naoya Horiguchi <n-horiguchi@...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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