linux-kernel - Re: [bad page] memcg: another bad page at page migration (2.6.26-rc5-mm3 + patch collection)

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Date:	Tue, 24 Jun 2008 12:22:57 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	linux-mm@...ck.org, balbir@...ux.vnet.ibm.com, xemul@...nvz.org,
	linux-kernel@...r.kernel.org
Subject: Re: [bad page] memcg: another bad page at page migration
 (2.6.26-rc5-mm3 + patch collection)

On Tue, 24 Jun 2008 10:37:09 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:

> > I don't use shmem explicitly, but I'll test this patch anyway
> > and report the result.
> > 
> Unfortunately, this patch doesn't solve my problem, hum...
> I'll dig more, too.
> In my test, I don't use large amount of memory, so I think
> no swap activities happens, perhaps.
> 
Sigh, one hint in the log is
==
Bad page state in process 'switch.sh'
page:ffffe2000c8e59c0 flags:0x0200000000080018 mapping:000
0000000000000 mapcount:0 count:0
cgroup:ffff81062a817050
==

- the page was mapped one.
- a page is swapbacked ....Anon or Shmem/tmpfs.
- mapping is NULL

When it was a *source* page.
   .. if it was Anon, page->mapping was cleared by migrate_page_copy()
   .. if not, replacement in radix-tree was succeeded.

When it was a destination page
   .. page-flags is copied, then, migrate_page_copy() was called.
   .. newpage->mapping is cleared only at migration failure.

Hmm..I think the troublesome page is *source* page now.

Anyway, thanks.
-Kame

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