linux-kernel - Re: [PATCH][RFC] fix kernel BUG at mm/migrate.c:719! in 2.6.26-rc5-mm3

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Date:	Wed, 18 Jun 2008 13:59:11 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kernel-testers@...r.kernel.org
Subject: Re: [PATCH][RFC] fix kernel BUG at mm/migrate.c:719! in
 2.6.26-rc5-mm3

On Wed, 18 Jun 2008 13:41:28 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:

> On Wed, 18 Jun 2008 10:54:00 +0900, Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:
> > On Wed, 18 Jun 2008 00:33:18 +0900, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> > > > @@ -715,13 +725,7 @@ unlock:
> > > >   		 * restored.
> > > >   		 */
> > > >   		list_del(&page->lru);
> > > > -		if (!page->mapping) {
> > > > -			VM_BUG_ON(page_count(page) != 1);
> > > > -			unlock_page(page);
> > > > -			put_page(page);		/* just free the old page */
> > > > -			goto end_migration;
> > > > -		} else
> > > > -			unlock = putback_lru_page(page);
> > > > +		unlock = putback_lru_page(page);
> > > >  	}
> > > >  
> > > >  	if (unlock)
> > > 
> > > this part is really necessary?
> > > I tryed to remove it, but any problem doesn't happend.
> > > 
> > I made this part first, and added a fix for migration_entry_wait later.
> > 
> > So, I haven't test without this part, and I think it will cause
> > VM_BUG_ON() here without this part.
> > 
> > Anyway, I will test it.
> > 
> I got this VM_BUG_ON() as expected only by doing:
> 
>   # echo $$ >/cgroup/cpuset/02/tasks
> 
> So, I beleive that both fixes for migration_entry_wait and
> unmap_and_move (and, of course, removal VM_BUG_ON from
> putback_lru_page) are needed.
> 
> 
yes, but I'm now trying to rewrite putback_lru_page(). For avoid more complication.

Thanks,
-Kame

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