linux-kernel - Re: [PATCH 4/4] memcg: fix rmdir, force

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Date:	Fri, 21 Jan 2011 08:41:51 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>
Subject: Re: [PATCH 4/4] memcg: fix rmdir, force_empty with THP

On Fri, 21 Jan 2011 08:39:30 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Thu, 20 Jan 2011 14:41:08 +0100
> Johannes Weiner <hannes@...xchg.org> wrote:
> 
> > On Tue, Jan 18, 2011 at 11:43:48AM +0900, KAMEZAWA Hiroyuki wrote:
> > > 
> > > Now, when THP is enabled, memcg's rmdir() function is broken
> > > because move_account() for THP page is not supported.
> > > 
> > > This will cause account leak or -EBUSY issue at rmdir().
> > > This patch fixes the issue by supporting move_account() THP pages.
> > > 
> > > Changelog:
> > >  - style fix.
> > >  - add compound_lock for avoiding races.
> > > 
> > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > > ---
> > >  mm/memcontrol.c |   37 ++++++++++++++++++++++++++-----------
> > >  1 file changed, 26 insertions(+), 11 deletions(-)
> > > 
> > > Index: mmotm-0107/mm/memcontrol.c
> > > ===================================================================
> > > --- mmotm-0107.orig/mm/memcontrol.c
> > > +++ mmotm-0107/mm/memcontrol.c
> > 
> > > @@ -2267,6 +2274,8 @@ static int mem_cgroup_move_parent(struct
> > >  	struct cgroup *cg = child->css.cgroup;
> > >  	struct cgroup *pcg = cg->parent;
> > >  	struct mem_cgroup *parent;
> > > +	int charge = PAGE_SIZE;
> > 
> > No need to initialize, you assign it unconditionally below.
> > 
> > It's also a bit unfortunate that the parameter/variable with this
> > meaning appears under a whole bunch of different names.  page_size,
> > charge_size, and now charge.  Could you stick with page_size?
> > 
> 
> charge_size != page_size.
> 
> Clean up as you like, later. I'll Ack.
> 
> > > @@ -2278,17 +2287,23 @@ static int mem_cgroup_move_parent(struct
> > >  		goto out;
> > >  	if (isolate_lru_page(page))
> > >  		goto put;
> > > +	/* The page is isolated from LRU and we have no race with splitting */
> > > +	charge = PAGE_SIZE << compound_order(page);
> > 
> > Why is LRU isolation preventing the splitting?
> > 
> 
> That's my mistake of comment, which was in the older patch.
> I use compound_lock now. I'll post clean up.
> 
It seems patches are sent to Linus's tree.

I'll post some clean up patches for memcontrol.c.
I hope that will not break other guy's works.

Thanks,
-kame


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