linux-kernel - Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb

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Message-ID: <20130410080706.GA20998@dhcp22.suse.cz>
Date:	Wed, 10 Apr 2013 10:07:06 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in
 follow_hugetlb_page()

On Tue 09-04-13 18:00:34, Naoya Horiguchi wrote:
[...]
> I rewrite the comment here, how about this?
> 
> -		if (absent ||
> +		/*
> +		 * We need call hugetlb_fault for both hugepages under migration
> +		 * (in which case hugetlb_fault waits for the migration,) and
> +		 * hwpoisoned hugepages (in which case we need to prevent the
> +		 * caller from accessing to them.) In order to do this, we use
> +		 * here is_swap_pte instead of is_hugetlb_entry_migration and
> +		 * is_hugetlb_entry_hwpoisoned. This is because it simply covers
> +		 * both cases, and because we can't follow correct pages directly
> +		 * from any kind of swap entries.
> +		 */
> +		if (absent || is_swap_pte(huge_ptep_get(pte)) ||
>  		    ((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) {
>  			int ret;

OK, thanks!

-- 
Michal Hocko
SUSE Labs
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