Re: [PATCH 3/4] powerpc/numa: set node_possible_map from node_online_map

[Yury Norov <yury.norov@gmail.com>]

On Thu, Jul 02, 2026 at 02:18:50AM +0900, Sang-Heon Jeon wrote:
> mem_topology_setup() intersects node_possible_map with node_online_map.
> Nothing sets node_possible_map before this, so it is NODE_MASK_ALL and
> the result is just node_online_map.
> 
> In preparation for changing node_possible_map's initial value,
> mem_topology_setup() no longer depends on it.
> 
> No functional change.
> 
> Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
> ---
>  arch/powerpc/mm/numa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index f4cf3ae036de..2fdecae90a01 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -1179,7 +1179,7 @@ void __init mem_topology_setup(void)
>  	 * that we expect to make use of for this platform's affinity
>  	 * calculations.
>  	 */
> -	nodes_and(node_possible_map, node_possible_map, node_online_map);
> +	node_possible_map = node_online_map;
>  
>  	find_possible_nodes();

And in find_possible_nodes():

         for (i = 0; i < max_nodes; i++) {
                 if (!node_possible(i))
                         node_set(i, node_possible_map);
         }

So, assuming the code reaches to that point, you unconditionally
online all the offlined nodes.

This doesn't look correct at the first glance, and definitely it's not
a "No functional change" type of things.