Re: [Bugme-new] [Bug 13690] New: nodes_clear cause hugepage unusableon non-NUMA machine

[Christoph Lameter]

On Thu, 2 Jul 2009, Yinghai Lu wrote:

> Index: linux-2.6/arch/x86/mm/init_64.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/mm/init_64.c
> +++ linux-2.6/arch/x86/mm/init_64.c
> @@ -598,8 +598,14 @@ void __init paging_init(void)
>
>  	sparse_memory_present_with_active_regions(MAX_NUMNODES);
>  	sparse_init();
> -	/* clear the default setting with node 0 */
> +#if MAX_NUMNODES > 1
> +	/*
> +	 * clear the default setting with node 0
> +	 * note: don't clear it, node_set_state will do nothing
> +	 *	 (aka set it back) when numa support is not compiled in
> +	 */
>  	nodes_clear(node_states[N_NORMAL_MEMORY]);

The problem was that nodes_clear() does not fall back to a noop on !NUMA.
The node_set/clear_states() operations do become noops.

Could we make it more consistent by using only operations of the same
type? F.e. Add a node_clearall_states() in include/linux/nodemask.h that
falls back to a noop on !NUMA like the node_*_states operation?

Another options is to restore node_states[N_NORMAL_MEMORY] to its
initial condition. See the definition of node_states in page_alloc.c.
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