linux-kernel - Re: [patch 13/13] mm: memcontrol: rewrite uncharge API

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Date:	Thu, 24 Jul 2014 11:02:57 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Miklos Szeredi <miklos@...redi.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, Tejun Heo <tj@...nel.org>,
	Vladimir Davydov <vdavydov@...allels.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org,
	Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch 13/13] mm: memcontrol: rewrite uncharge API

On Thu 24-07-14 10:46:44, Michal Hocko wrote:
> On Wed 23-07-14 17:02:41, Johannes Weiner wrote:
[...]
> We can reduce the lookup only to lruvec==true case, no?

Dohh
s@can@...uld@

newpage shouldn't charged in all other cases and it would be bug.
Or am I missing something?

> Acked-by: Michal Hocko <mhocko@...e.cz>
> 
> > ---
> >  mm/memcontrol.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index b7c9a202dee9..3eaa6e83c168 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -6660,6 +6660,12 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
> >  	if (mem_cgroup_disabled())
> >  		return;
> >  
> > +	/* Page cache replacement: new page already charged? */
> > +	pc = lookup_page_cgroup(newpage);
> > +	if (PageCgroupUsed(pc))
> > +		return;
> > +
> > +	/* Re-entrant migration: old page already uncharged? */
> >  	pc = lookup_page_cgroup(oldpage);
> >  	if (!PageCgroupUsed(pc))
> >  		return;
> > -- 
> > 2.0.0
> > 
> 
> -- 
> Michal Hocko
> SUSE Labs
> 
> --
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-- 
Michal Hocko
SUSE Labs
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