linux-kernel - Re: [patch 1/3] mm: memcontrol: take a css reference for each charged page

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Message-ID: <20141008132927.GC4592@dhcp22.suse.cz>
Date:	Wed, 8 Oct 2014 15:29:27 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	linux-mm@...ck.org, Vladimir Davydov <vdavydov@...allels.com>,
	Greg Thelen <gthelen@...gle.com>, Tejun Heo <tj@...nel.org>,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/3] mm: memcontrol: take a css reference for each
 charged page

On Wed 08-10-14 15:27:54, Michal Hocko wrote:
> On Sat 20-09-14 16:00:33, Johannes Weiner wrote:
[...]
> > @@ -2803,8 +2808,10 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg,
> >  		page_counter_uncharge(&memcg->memsw, nr_pages);
> >  
> 
> Wouldn't a single out_css_put be more readable? I was quite confused
> when I start reading the patch before I saw the next hunk.

Ohh, this will go away in the next patch. Ignore this.

> 
> >  	/* Not down to 0 */
> > -	if (page_counter_uncharge(&memcg->kmem, nr_pages))
> 		goto out_css_put;
> 
> > +	if (page_counter_uncharge(&memcg->kmem, nr_pages)) {
> > +		css_put_many(&memcg->css, nr_pages);
> >  		return;
> > +	}
> >  
> >  	/*
> >  	 * Releases a reference taken in kmem_cgroup_css_offline in case
> > @@ -2816,6 +2823,8 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg,
> >  	 */
> >  	if (memcg_kmem_test_and_clear_dead(memcg))
> >  		css_put(&memcg->css);
> > +
> 
> out_css_put:
> > +	css_put_many(&memcg->css, nr_pages);
> >  }
> >  
> >  /*
> -- 
> Michal Hocko
> SUSE Labs

-- 
Michal Hocko
SUSE Labs
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