Re: [PATCH v2 1/2][BUGFIX] mm: do not use page_count without a page pin

[Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>]

(2012/06/14 10:12), Minchan Kim wrote:
> d179e84ba fixed the problem[1] in vmscan.c but same problem is here.
> Let's fix it.
> 
> [1] http://comments.gmane.org/gmane.linux.kernel.mm/65844
> 
> I copy and paste d179e84ba's contents for description.
> 
> "It is unsafe to run page_count during the physical pfn scan because
> compound_head could trip on a dangling pointer when reading
> page->first_page if the compound page is being freed by another CPU."
> 
> * changelog from v1
>    - Add comment about skip tail page of THP - Andrea
>    - fix typo - Wanpeng Li
>    - based on next-20120613
> 
> Cc: Andrea Arcangeli<aarcange@xxxxxxxxxx>
> Cc: Mel Gorman<mgorman@xxxxxxx>
> Cc: Michal Hocko<mhocko@xxxxxxx>
> Cc: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Cc: Wanpeng Li<liwp.linux@xxxxxxxxx>
> Signed-off-by: Minchan Kim<minchan@xxxxxxxxxx>

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

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