Re: [06/44] numa: fix slab_node(MPOL_BIND)

From: Lee Schermerhorn
Date: Tue Dec 07 2010 - 22:03:29 EST


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@xxxxxxxxx>
>
> 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@xxxxxxxxx>
> Cc: Mel Gorman <mel@xxxxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
>
> ---
> 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.

Lee

> }
>
> default:
>
>




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