Re: [RFC PATCH V6 13/19] memory-hotplug: check page type in get_page_bootmem

[Wen Congyang <wency@cn.fujitsu.com>]

At 08/03/2012 03:49 PM, wency@cn.fujitsu.com Wrote:
> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> 
> There is a possibility that get_page_bootmem() is called to the same page many
> times. So when get_page_bootmem is called to the same page, the function only
> increments page->_count.
> 
> CC: David Rientjes <rientjes@google.com>
> CC: Jiang Liu <liuj97@gmail.com>
> CC: Len Brown <len.brown@intel.com>
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> CC: Christoph Lameter <cl@linux.com>
> Cc: Minchan Kim <minchan.kim@gmail.com>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> CC: Wen Congyang <wency@cn.fujitsu.com>
> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> ---
>  mm/memory_hotplug.c |   15 +++++++++++----
>  1 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 5f9f8c7..710e593 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -95,10 +95,17 @@ static void release_memory_resource(struct resource *res)
>  static void get_page_bootmem(unsigned long info,  struct page *page,
>  			     unsigned long type)
>  {
> -	page->lru.next = (struct list_head *) type;
> -	SetPagePrivate(page);
> -	set_page_private(page, info);
> -	atomic_inc(&page->_count);
> +	unsigned long page_type;
> +
> +	page_type = (unsigned long) page->lru.next;
> +	if (type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
> +	    type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE){

I think it should be page_type not type here.

Thanks
Wen Congyang

> +		page->lru.next = (struct list_head *) type;
> +		SetPagePrivate(page);
> +		set_page_private(page, info);
> +		atomic_inc(&page->_count);
> +	} else
> +		atomic_inc(&page->_count);
>  }
>  
>  /* reference to __meminit __free_pages_bootmem is valid