Re: [patch 7/9] mm: memcontrol: do not acquire page_cgroup lock for kmem pages

[Michal Hocko]

On Tue 27-05-14 15:53:42, Johannes Weiner wrote:
> On Fri, May 23, 2014 at 03:39:38PM +0200, Michal Hocko wrote:
[...]
> > >  	if (!PageCgroupUsed(pc))
> > >  		return;
> > >  
> > > -	lock_page_cgroup(pc);
> > > -	if (PageCgroupUsed(pc)) {
> > > -		memcg = pc->mem_cgroup;
> > > -		ClearPageCgroupUsed(pc);
> > > -	}
> > > -	unlock_page_cgroup(pc);
> > 
> > maybe add
> > 	WARN_ON_ONCE(pc->flags != PCG_USED);
> > 
> > to check for an unexpected flags usage in the kmem path?
> 
> There is no overlap between page types that use PCG_USED and those
> that don't.  What would be the value of adding this?

I meant it as an early warning that something bad is going on.

-- 
Michal Hocko
SUSE Labs
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