linux-kernel - Re: [RFC][PATCH 4/6] memcg: swap cgroup for remembering account

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Date:	Wed, 12 Nov 2008 13:22:19 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	nishimura@....nes.nec.co.jp
Cc:	Daisuke Nishimura <d-nishimura@....biglobe.ne.jp>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"menage@...gle.com" <menage@...gle.com>
Subject: Re: [RFC][PATCH 4/6] memcg: swap cgroup for remembering account

On Wed, 12 Nov 2008 13:17:01 +0900
Daisuke Nishimura <d-nishimura@....biglobe.ne.jp> wrote:

> > +/**
> > + * lookup_swap_cgroup - lookup mem_cgroup tied to swap entry
> > + * @ent: swap entry to be looked up.
> > + *
> > + * Returns pointer to mem_cgroup at success. NULL at failure.
> > + */
> > +struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent)
> > +{
> > +	int type = swp_type(ent);
> > +	unsigned long flags;
> > +	unsigned long offset = swp_offset(ent);
> > +	unsigned long idx = offset / SC_PER_PAGE;
> > +	unsigned long pos = offset & SC_POS_MASK;
> > +	struct swap_cgroup_ctrl *ctrl;
> > +	struct page *mappage;
> > +	struct swap_cgroup *sc;
> > +	struct mem_cgroup *ret;
> > +
> > +	if (!do_swap_account)
> > +		return NULL;
> > +
> > +	ctrl = &swap_cgroup_ctrl[type];
> > +
> > +	mappage = ctrl->map[idx];
> > +
> > +	spin_lock_irqsave(&ctrl->lock, flags);
> > +	sc = kmap_atomic(mappage, KM_USER0);
> > +	sc += pos;
> > +	ret = sc->val;
> > +	kunmap_atomic(mapppage, KM_USER0);
> s/mapppage/mappage
> 
> I don't know why I didn't notice this while testing previous version.
> 
Ah...kmap_atomic() doesn't check its argument if HIGHMEM=n.
and mapppage disappears by macro.

I'm now preparing x86-32 test enviroment before goint further.

Thanks,
-Kame

> 
> Thanks,
> Daisuke Nishimura.
> 
> > +	spin_unlock_irqrestore(&ctrl->lock, flags);
> > +	return ret;
> > +}
> > +
> 

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