Re: [PATCH 1/2] mm: Mark nr_node_ids __ro_after_init

[Mike Rapoport <rppt@kernel.org>]

On Wed, Aug 02, 2023 at 01:24:59PM +0200, Peter Zijlstra wrote:
> Just like nr_cpu_ids, nr_node_ids covers the side of possible_map and
> is thus constant after init.
> 
> Mark the variable __ro_after_init to both improve performance and
> enhance security, since the variable is exported. A module writing to
> it would be 'unfortunate'.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>

> ---
>  mm/page_alloc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -305,7 +305,7 @@ int movable_zone;
>  EXPORT_SYMBOL(movable_zone);
>  
>  #if MAX_NUMNODES > 1
> -unsigned int nr_node_ids __read_mostly = MAX_NUMNODES;
> +unsigned int nr_node_ids __ro_after_init = MAX_NUMNODES;
>  unsigned int nr_online_nodes __read_mostly = 1;
>  EXPORT_SYMBOL(nr_node_ids);
>  EXPORT_SYMBOL(nr_online_nodes);
> 
> 

-- 
Sincerely yours,
Mike.