linux-kernel - Re: [PATCH 08/14] mm, compaction: skip over holes in __reset_isolation

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Date:   Fri, 19 May 2017 09:23:33 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, Mel Gorman <mgorman@...e.de>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 08/14] mm, compaction: skip over holes in
 __reset_isolation_suitable

On 05/15/2017 10:58 AM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> __reset_isolation_suitable walks the whole zone pfn range and it tries
> to jump over holes by checking the zone for each page. It might still
> stumble over offline pages, though. Skip those by checking
> pfn_to_online_page()
> 
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/compaction.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 613c59e928cb..fb548e4c7bd4 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -236,10 +236,9 @@ static void __reset_isolation_suitable(struct zone *zone)
>  
>  		cond_resched();
>  
> -		if (!pfn_valid(pfn))
> +		page = pfn_to_online_page(pfn);
> +		if (!page)
>  			continue;
> -
> -		page = pfn_to_page(pfn);
>  		if (zone != page_zone(page))
>  			continue;
>  
>