linux-kernel - Re: [PATCH 1/2] mm: refactor out __alloc_contig_migrate

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Date:	Fri, 14 Sep 2012 14:32:22 +0800
From:	Wen Congyang <wency@...fujitsu.com>
To:	Minchan Kim <minchan@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH 1/2] mm: refactor out __alloc_contig_migrate_alloc

At 09/12/2012 09:43 AM, Minchan Kim Wrote:
> __alloc_contig_migrate_alloc can be used by memory-hotplug so
> refactor out(move + rename as a common name) it into
> page_isolation.c.
> 
> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> Cc: Michal Nazarewicz <mina86@...a86.com>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Wen Congyang <wency@...fujitsu.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
> 
> This patch is intended for preparing next bug fix patch.
> 
>  include/linux/page-isolation.h |    3 ++-
>  mm/page_alloc.c                |   14 +-------------
>  mm/page_isolation.c            |   11 +++++++++++
>  3 files changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
> index 105077a..1c82261 100644
> --- a/include/linux/page-isolation.h
> +++ b/include/linux/page-isolation.h
> @@ -37,6 +37,7 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn);
>   */
>  int set_migratetype_isolate(struct page *page);
>  void unset_migratetype_isolate(struct page *page, unsigned migratetype);
> -
> +struct page *alloc_migrate_target(struct page *page, unsigned long private,
> +				int **resultp);
>  
>  #endif
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a4ff74e..6716023 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5648,18 +5648,6 @@ static unsigned long pfn_max_align_up(unsigned long pfn)
>  				pageblock_nr_pages));
>  }
>  
> -static struct page *
> -__alloc_contig_migrate_alloc(struct page *page, unsigned long private,
> -			     int **resultp)
> -{
> -	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
> -
> -	if (PageHighMem(page))
> -		gfp_mask |= __GFP_HIGHMEM;
> -
> -	return alloc_page(gfp_mask);
> -}
> -
>  /* [start, end) must belong to a single zone. */
>  static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
>  {
> @@ -5700,7 +5688,7 @@ static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
>  		}
>  
>  		ret = migrate_pages(&cc.migratepages,
> -				    __alloc_contig_migrate_alloc,
> +				    alloc_migrate_target,
>  				    0, false, MIGRATE_SYNC);
>  	}
>  
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 247d1f1..6936545 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -233,3 +233,14 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
>  	spin_unlock_irqrestore(&zone->lock, flags);
>  	return ret ? 0 : -EBUSY;
>  }
> +
> +struct page *alloc_migrate_target(struct page *page, unsigned long private,
> +                             int **resultp)
> +{
> +        gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
> +
> +        if (PageHighMem(page))
> +                gfp_mask |= __GFP_HIGHMEM;
> +
> +        return alloc_page(gfp_mask);

alloc_page() will use current task's memory policy. If we offline memory like this:
numactl -m n echo offline >/sys/devices/system/memory/memoryX/state # n is page's nid

It may trigger OOM event.

Thanks
Wen Congyang

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