linux-kernel - Re: [PATCH -mmotm 1/5] memcg: disable irq at page cgroup lock

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Date:	Mon, 15 Mar 2010 11:00:25 +0100
From:	Andrea Righi <arighi@...eler.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Trond Myklebust <trond.myklebust@....uio.no>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Andrew Morton <akpm@...ux-foundation.org>,
	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH -mmotm 1/5] memcg: disable irq at page cgroup lock

On Mon, Mar 15, 2010 at 09:06:38AM +0900, KAMEZAWA Hiroyuki wrote:
> On Mon, 15 Mar 2010 00:26:38 +0100
> Andrea Righi <arighi@...eler.com> wrote:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > 
> > Now, file-mapped is maintaiend. But more generic update function
> > will be needed for dirty page accounting.
> > 
> > For accountig page status, we have to guarantee lock_page_cgroup()
> > will be never called under tree_lock held.
> > To guarantee that, we use trylock at updating status.
> > By this, we do fuzzy accounting, but in almost all case, it's correct.
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> Bad patch title...."use trylock for safe accounting in some contexts" ?

OK, sounds better. I just copy & paste the email subject, but the title
was probably related to the old lock_page_cgroup()+irq_disable patch.

Thanks,
-Andrea
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