linux-kernel - Re: [06/44] numa: fix slab_node(MPOL

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Message-ID: <1291816467.3941.19.camel@zaphod>
Date:	Wed, 08 Dec 2010 08:54:27 -0500
From:	Lee Schermerhorn <Lee.Schermerhorn@...com>
To:	Greg KH <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mel Gorman <mel@....ul.ie>, Christoph Lameter <cl@...ux.com>
Subject: Re: [06/44] numa: fix slab_node(MPOL_BIND)

On Tue, 2010-12-07 at 20:17 -0800, Greg KH wrote:
> On Tue, Dec 07, 2010 at 10:03:42PM -0500, Lee Schermerhorn wrote:
> > On Tue, 2010-12-07 at 16:04 -0800, Greg KH wrote:
> > > 2.6.27-stable review patch.  If anyone has any objections, please let us know.
> > > 
> > > ------------------
> > > 
> > > From: Eric Dumazet <eric.dumazet@...il.com>
> > > 
> > > commit 800416f799e0723635ac2d720ad4449917a1481c upstream.
> > > 
> > > When a node contains only HighMem memory, slab_node(MPOL_BIND)
> > > dereferences a NULL pointer.
> > > 
> > > [ This code seems to go back all the way to commit 19770b32609b: "mm:
> > >   filter based on a nodemask as well as a gfp_mask".  Which was back in
> > >   April 2008, and it got merged into 2.6.26.  - Linus ]
> > > 
> > > Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> > > Cc: Mel Gorman <mel@....ul.ie>
> > > Cc: Christoph Lameter <cl@...ux.com>
> > > Cc: Lee Schermerhorn <lee.schermerhorn@...com>
> > > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > > Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> > > 
> > > ---
> > >  mm/mempolicy.c |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > --- a/mm/mempolicy.c
> > > +++ b/mm/mempolicy.c
> > > @@ -1404,7 +1404,7 @@ unsigned slab_node(struct mempolicy *pol
> > >  		(void)first_zones_zonelist(zonelist, highest_zoneidx,
> > >  							&policy->v.nodes,
> > >  							&zone);
> > > -		return zone->node;
> > > +		return zone ? zone->node : numa_node_id();
> > 
> > I think this should be numa_mem_id().  Given the documented purpose of
> > slab_node(), we want a node from which page allocation is likely to
> > succeed.  numa_node_id() can return a memoryless node for, e.g.,  some
> > configurations of some HP ia64 platforms.  numa_mem_id() was introduced
> > to return that same node from which "local" mempolicy would allocate
> > pages.
> 
> So should the upstream patch be changed?
> 

Yeah, probably should.  I didn't see it go by.

Lee

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