linux-kernel - Re: [patch 2/9] mm: memcontrol: rearrange charging fast path

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Message-ID: <20140512075938.GB9564@dhcp22.suse.cz>
Date:	Mon, 12 May 2014 09:59:38 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	linux-mm@...ck.org, Hugh Dickins <hughd@...gle.com>,
	Tejun Heo <tj@...nel.org>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 2/9] mm: memcontrol: rearrange charging fast path

On Thu 08-05-14 14:22:24, Johannes Weiner wrote:
> On Wed, May 07, 2014 at 04:33:34PM +0200, Michal Hocko wrote:
> > On Wed 30-04-14 16:25:36, Johannes Weiner wrote:
[...]
> > > -	if (unlikely(task_in_memcg_oom(current)))
> > > -		goto nomem;
> > > -
> > > -	if (gfp_mask & __GFP_NOFAIL)
> > > -		oom = false;
> > >  retry:
> > >  	if (consume_stock(memcg, nr_pages))
> > >  		goto done;
> > [...]
> > > @@ -2662,6 +2660,9 @@ retry:
> > >  	if (mem_cgroup_wait_acct_move(mem_over_limit))
> > >  		goto retry;
> > >  
> > > +	if (gfp_mask & __GFP_NOFAIL)
> > > +		goto bypass;
> > > +
> > 
> > This is a behavior change because we have returned ENOMEM previously
> 
> __GFP_NOFAIL must never return -ENOMEM, or we'd have to rename it ;-)
> It just looks like this in the patch, but this is the label code:
> 
> nomem:
> 	if (!(gfp_mask & __GFP_NOFAIL))
> 		return -ENOMEM;
> bypass:
> 	...

Ouch. Brain fart. Sorry...

-- 
Michal Hocko
SUSE Labs
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