linux-kernel - Re: [PATCH] memory hotplug: fix page_zone() calculation in test_pages

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Message-Id: <20081030090958.f86d49db.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 30 Oct 2008 09:09:58 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	gerald.schaefer@...ibm.com
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com, y-goto@...fujitsu.com,
	dave@...ux.vnet.ibm.com
Subject: Re: [PATCH] memory hotplug: fix page_zone() calculation in
 test_pages_isolated()

On Wed, 29 Oct 2008 15:25:30 +0100
Gerald Schaefer <gerald.schaefer@...ibm.com> wrote:

> From: Gerald Schaefer <gerald.schaefer@...ibm.com>
> 
> My last bugfix here (adding zone->lock) introduced a new problem: Using
> page_zone(pfn_to_page(pfn)) to get the zone after the for() loop is wrong.
> pfn will then be >= end_pfn, which may be in a different zone or not
> present at all. This may lead to an addressing exception in page_zone()
> or spin_lock_irqsave().
> 
> Now I use __first_valid_page() again after the loop to find a valid page
> for page_zone().
> 
> Signed-off-by: Gerald Schaefer <gerald.schaefer@...ibm.com>
> 
Thanks.

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

> ---
>  mm/page_isolation.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6/mm/page_isolation.c
> ===================================================================
> --- linux-2.6.orig/mm/page_isolation.c
> +++ linux-2.6/mm/page_isolation.c
> @@ -130,10 +130,11 @@ int test_pages_isolated(unsigned long st
>  		if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
>  			break;
>  	}
> -	if (pfn < end_pfn)
> +	page = __first_valid_page(start_pfn, end_pfn - start_pfn);
> +	if ((pfn < end_pfn) || !page)
>  		return -EBUSY;
>  	/* Check all pages are free or Marked as ISOLATED */
> -	zone = page_zone(pfn_to_page(pfn));
> +	zone = page_zone(page);
>  	spin_lock_irqsave(&zone->lock, flags);
>  	ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn);
>  	spin_unlock_irqrestore(&zone->lock, flags);
> 
> 

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