linux-kernel - Re: [ 39/40] cpuset: mm: reduce large amounts of memory barrier related damage v3

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Date:	Fri, 27 Jul 2012 16:23:47 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Miao Xie <miaox@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [ 39/40] cpuset: mm: reduce large amounts of memory barrier
 related damage v3

> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -1457,6 +1457,7 @@ static struct page *get_any_partial(stru
> >  	struct zone *zone;
> >  	enum zone_type high_zoneidx = gfp_zone(flags);
> >  	struct page *page;
> > +	unsigned int cpuset_mems_cookie;
> >  
> >  	/*
> >  	 * The defrag ratio allows a configuration of the tradeoffs between
> > @@ -1480,22 +1481,32 @@ static struct page *get_any_partial(stru
> >  			get_cycles() % 1024 > s->remote_node_defrag_ratio)
> >  		return NULL;
> >  
> > -	get_mems_allowed();
> > -	zonelist = node_zonelist(slab_node(current->mempolicy), flags);
> > -	for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
> > -		struct kmem_cache_node *n;
> > +	do {
> > +		cpuset_mems_cookie = get_mems_allowed();
> > +		zonelist = node_zonelist(slab_node(current->mempolicy), flags);
> > +		for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
> > +			struct kmem_cache_node *n;
> >  
> > -		n = get_node(s, zone_to_nid(zone));
> > +			n = get_node(s, zone_to_nid(zone));
> >  
> > -		if (n && cpuset_zone_allowed_hardwall(zone, flags) &&
> > -				n->nr_partial > s->min_partial) {
> > -			page = get_partial_node(n);
> > -			if (page) {
> > -				put_mems_allowed();
> > -				return page;
> > +			if (n && cpuset_zone_allowed_hardwall(zone, flags) &&
> > +					n->nr_partial > s->min_partial) {
> > +				page = get_partial_node(n);
> > +				if (page) {
> > +					/*
> > +					 * Return the object even if
> > +					 * put_mems_allowed indicated that
> > +					 * the cpuset mems_allowed was
> > +					 * updated in parallel. It's a
> > +					 * harmless race between the alloc
> > +					 * and the cpuset update.
> > +					 */
> > +					put_mems_allowed(cpuset_mems_cookie);
> > +					return page;
> > +				}
> >  			}
> >  		}
> > -	}
> > +	} while (!put_mems_allowed(cpuset_mems_cookie));
> >  	put_mems_allowed();
> 
> This doesn't build on 3.0, the backport left the stray put_mems_allowed
> above:
> 
> linux-stable/mm/slub.c: In function 'get_any_partial':
> linux-stable/mm/slub.c:1510:2: error: too few arguments to function 'put_mems_allowed'
> linux-stable/include/linux/cpuset.h:108:20: note: declared here
> 

That line should have been deleted and tests were based on slab. My
apologies.

---8<---
cpuset: mm: Reduce large amounts of memory barrier related damage fix

linux-stable/mm/slub.c: In function 'get_any_partial':
linux-stable/mm/slub.c:1510:2: error: too few arguments to function 'put_mems_allowed'
linux-stable/include/linux/cpuset.h:108:20: note: declared here

Reported-by: Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
Signed-off-by: Mel Gorman <mgorman@...e.de>

diff --git a/mm/slub.c b/mm/slub.c
index 00ccf2c..ae6e80e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1507,7 +1507,6 @@ static struct page *get_any_partial(struct kmem_cache *s, gfp_t flags)
 			}
 		}
 	} while (!put_mems_allowed(cpuset_mems_cookie));
-	put_mems_allowed();
 #endif
 	return NULL;
 }
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