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

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Date:	Tue, 15 Jul 2014 18:07:35 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	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, linux-kernel@...r.kernel.org
Subject: Re: [patch 13/13] mm: memcontrol: rewrite uncharge API

On Tue 15-07-14 11:55:37, Naoya Horiguchi wrote:
> On Wed, Jun 18, 2014 at 04:40:45PM -0400, Johannes Weiner wrote:
> ...
> > diff --git a/mm/swap.c b/mm/swap.c
> > index a98f48626359..3074210f245d 100644
> > --- a/mm/swap.c
> > +++ b/mm/swap.c
> > @@ -62,6 +62,7 @@ static void __page_cache_release(struct page *page)
> >  		del_page_from_lru_list(page, lruvec, page_off_lru(page));
> >  		spin_unlock_irqrestore(&zone->lru_lock, flags);
> >  	}
> > +	mem_cgroup_uncharge(page);
> >  }
> >  
> >  static void __put_single_page(struct page *page)
> 
> This seems to cause a list breakage in hstate->hugepage_activelist
> when freeing a hugetlbfs page.

This looks like a fall out from
http://marc.info/?l=linux-mm&m=140475936311294&w=2

I didn't get to review this one but the easiest fix seems to be check
HugePage and do not call uncharge.

> For hugetlbfs, we uncharge in free_huge_page() which is called after
> __page_cache_release(), so I think that we don't have to uncharge here.
> 
> In my testing, moving mem_cgroup_uncharge() inside if (PageLRU) block
> fixed the problem, so if that works for you, could you fold the change
> into your patch?
> 
> Thanks,
> Naoya Horiguchi
> 
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-- 
Michal Hocko
SUSE Labs
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