Date: Fri, 27 Jun 2008 14:41:00 +0900
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: "MinChan Kim" <minchan.kim@gmail.com>
Subject: Re: [-mm][PATCH 8/10] fix shmem page migration incorrectness on memcgroup
Cc: kosaki.motohiro@jp.fujitsu.com,
       "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>,
       LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       "Lee Schermerhorn" <Lee.Schermerhorn@hp.com>,
       "Rik van Riel" <riel@redhat.com>,
       "Daisuke Nishimura" <nishimura@mxp.nes.nec.co.jp>
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References: <20080625190750.D864.KOSAKI.MOTOHIRO@jp.fujitsu.com> <28c262360806262208i6791d67at446f7323ded16206@mail.gmail.com>
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> > mem_cgroup_uncharge() against old page is done after radix-tree-replacement.
> > And there were special handling to ingore swap-cache page. But, shmem can
> > be swap-cache and file-cache at the same time. Chekcing PageSwapCache() is
> > not correct here. Check PageAnon() instead.
> 
> When/How shmem can be both swap-cache and file-cache ?
> I can't understand that situation.

Hi

see, 

shmem_writepage()
   -> add_to_swap_cache()
      -> SetPageSwapCache()


BTW: his file-cache mean !Anon, not mean !SwapBacked.


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