linux-kernel - Re: [PATCH] mm/hugetlb: use pmd_page() in follow_huge

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Date:	Fri, 10 Apr 2015 00:08:42 +0000
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Gerald Schaefer <gerald.schaefer@...ibm.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Michal Hocko <mhocko@...e.cz>,
	Andrea Arcangeli <aarcange@...hat.com>,
	"Martin Schwidefsky" <schwidefsky@...ibm.com>
Subject: Re: [PATCH] mm/hugetlb: use pmd_page() in follow_huge_pmd()

On Thu, Apr 09, 2015 at 06:11:35PM +0200, Gerald Schaefer wrote:
> commit 61f77eda "mm/hugetlb: reduce arch dependent code around follow_huge_*"
> broke follow_huge_pmd() on s390, where pmd and pte layout differ and using
> pte_page() on a huge pmd will return wrong results. Using pmd_page() instead
> fixes this.
> 
> All architectures that were touched by commit 61f77eda have pmd_page()
> defined, so this should not break anything on other architectures.
> 
> Signed-off-by: Gerald Schaefer <gerald.schaefer@...ibm.com>

Thank you for the report. This looks good to me.

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

> Cc: stable@...r.kernel.org # v3.12
> ---
>  mm/hugetlb.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e8c92ae..271e443 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3865,8 +3865,7 @@ retry:
>  	if (!pmd_huge(*pmd))
>  		goto out;
>  	if (pmd_present(*pmd)) {
> -		page = pte_page(*(pte_t *)pmd) +
> -			((address & ~PMD_MASK) >> PAGE_SHIFT);
> +		page = pmd_page(*pmd) + ((address & ~PMD_MASK) >> PAGE_SHIFT);
>  		if (flags & FOLL_GET)
>  			get_page(page);
>  	} else {
> -- 
> 2.1.4
> --
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