From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH 1/7] res_counter: add a function
 res_counter_move_parent().
Date: Wed, 18 Apr 2012 10:03:37 -0700
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To: KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
Cc: "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>, "cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>, Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>

On Wed, Apr 18, 2012 at 04:04:42PM +0900, KAMEZAWA Hiroyuki wrote:
> (2012/04/17 7:31), Tejun Heo wrote:
> 
> > On Thu, Apr 12, 2012 at 08:20:06PM +0900, KAMEZAWA Hiroyuki wrote:
> >> +/*
> >> + * In hierarchical accounting, child's usage is accounted into ancestors.
> >> + * To move local usage to its parent, just forget current level usage.
> >> + */
> >> +void res_counter_move_parent(struct res_counter *counter, unsigned long val)
> >> +{
> >> +	unsigned long flags;
> >> +
> >> +	BUG_ON(!counter->parent);
> >> +	spin_lock_irqsave(&counter->lock, flags);
> >> +	res_counter_uncharge_locked(counter, val);
> >> +	spin_unlock_irqrestore(&counter->lock, flags);
> >> +}
> > 
> > On the second thought, do we need this at all?  It's as good as doing
> > nothing after all, no?
> > 
> 
> 
> I considered that, but I think it may make it hard to debug memcg leakage.
> I'd like to confirm res->usage == 0 at removal of memcg.

Hmmm... then let's name it res_counter_reset() or something.  I feel
very confused about the function name.

Thanks.

-- 
tejun