Date: Mon, 22 Feb 2010 19:00:14 +0100
From: Andrea Righi <arighi@develer.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>,
       Suleiman Souhlal <suleiman@google.com>, Vivek Goyal <vgoyal@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] memcg: dirty pages accounting and limiting
 infrastructure
Message-ID: <20100222180013.GB4052@linux>
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 <20100222092242.98df82e4.kamezawa.hiroyu@jp.fujitsu.com>
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On Mon, Feb 22, 2010 at 09:22:42AM +0900, KAMEZAWA Hiroyuki wrote:

[snip]

> > +static unsigned long get_dirty_bytes(struct mem_cgroup *memcg)
> > +{
> > +	struct cgroup *cgrp = memcg->css.cgroup;
> > +	unsigned long dirty_bytes;
> > +
> > +	/* root ? */
> > +	if (cgrp->parent == NULL)
> > +		return vm_dirty_bytes;
> 
> We have mem_cgroup_is_root() macro.
> 
> > +
> > +	spin_lock(&memcg->reclaim_param_lock);
> > +	dirty_bytes = memcg->dirty_bytes;
> > +	spin_unlock(&memcg->reclaim_param_lock);
> > +
> > +	return dirty_bytes;
> > +}
> Hmm...do we need spinlock ? You use "unsigned long", then, read-write
> is always atomic if not read-modify-write.

I think I simply copy&paste the memcg->swappiness case. But I agree,
read-write should be atomic.

-Andrea
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