Re: [PATCH] HWPOISON: fix wrong num_poisoned_pages in handling memory error on thp

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 31 Jan 2013 10:25:58 -0500
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:

> num_poisoned_pages counts up the number of pages isolated by memory errors.
> But for thp, only one subpage is isolated because memory error handler
> splits it, so it's wrong to add (1 << compound_trans_order).
> 
> ...
>
> --- mmotm-2013-01-23-17-04.orig/mm/memory-failure.c
> +++ mmotm-2013-01-23-17-04/mm/memory-failure.c
> @@ -1039,7 +1039,14 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
>  		return 0;
>  	}
>  
> -	nr_pages = 1 << compound_trans_order(hpage);
> +	/*
> +	 * If a thp is hit by a memory failure, it's supposed to be split.
> +	 * So we should add only one to num_poisoned_pages for that case.
> +	 */
> +	if (PageHuge(p))

/*
 * PageHuge() only returns true for hugetlbfs pages, but not for normal or
 * transparent huge pages.  See the PageTransHuge() documentation for more
 * details.
 */
int PageHuge(struct page *page)
{


> +		nr_pages = 1 << compound_trans_order(hpage);
> +	else /* normal page or thp */
> +		nr_pages = 1;
>  	atomic_long_add(nr_pages, &num_poisoned_pages);
>  
>  	/*

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