Subject: Re: [PATCH 01/10] x86/mm/numa: Remove uninitialized_var() usage

From: Thomas Gleixner <[email-masked]>
Date: Thu, 04 Jun 2020 09:58:07 +0200

Kees Cook <[email-masked]> writes:
> -#ifdef NODE_NOT_IN_PAGE_FLAGS
> -	pfn_align = node_map_pfn_alignment();
> -	if (pfn_align && pfn_align < PAGES_PER_SECTION) {
> -		printk(KERN_WARNING "Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
> -		       PFN_PHYS(pfn_align) >> 20,
> -		       PFN_PHYS(PAGES_PER_SECTION) >> 20);
> -		return -EINVAL;
> +	if (IS_ENABLED(NODE_NOT_IN_PAGE_FLAGS)) {

Hrm, clever ...

> +		unsigned long pfn_align = node_map_pfn_alignment();
> +
> +		if (pfn_align && pfn_align < PAGES_PER_SECTION) {
> +			pr_warn("Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
> +				PFN_PHYS(pfn_align) >> 20,
> +				PFN_PHYS(PAGES_PER_SECTION) >> 20);
> +			return -EINVAL;
> +		}
>  	}
> -#endif
>  	if (!numa_meminfo_cover_memory(mi))
>  		return -EINVAL;
>  
> diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h
> index 71283739ffd2..1a4cdec2bd29 100644
> --- a/include/linux/page-flags-layout.h
> +++ b/include/linux/page-flags-layout.h
> @@ -100,7 +100,7 @@
>   * there.  This includes the case where there is no node, so it is implicit.
>   */
>  #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
> -#define NODE_NOT_IN_PAGE_FLAGS
> +#define NODE_NOT_IN_PAGE_FLAGS 1

but if we ever lose the 1 then the above will silently compile the code
within the IS_ENABLED() section out.

Thanks,

        tglx