Re: [PATCH v5 1/5] mm: introduce debug_pagealloc_{map,unmap}_pages() helpers

[Vlastimil Babka]

On 11/8/20 7:57 AM, Mike Rapoport wrote:
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1428,21 +1428,19 @@ static bool is_debug_pagealloc_cache(struct kmem_cache *cachep)
>   	return false;
>   }
>   
> -#ifdef CONFIG_DEBUG_PAGEALLOC
>   static void slab_kernel_map(struct kmem_cache *cachep, void *objp, int map)
>   {
>   	if (!is_debug_pagealloc_cache(cachep))
>   		return;

Hmm, I didn't notice earlier, sorry.
The is_debug_pagealloc_cache() above includes a debug_pagealloc_enabled_static() 
check, so it should be fine to use
__kernel_map_pages() directly below. Otherwise we generate two static key checks 
for the same key needlessly.

>   
> -	kernel_map_pages(virt_to_page(objp), cachep->size / PAGE_SIZE, map);
> +	if (map)
> +		debug_pagealloc_map_pages(virt_to_page(objp),
> +					  cachep->size / PAGE_SIZE);
> +	else
> +		debug_pagealloc_unmap_pages(virt_to_page(objp),
> +					    cachep->size / PAGE_SIZE);
>   }
>   
> -#else
> -static inline void slab_kernel_map(struct kmem_cache *cachep, void *objp,
> -				int map) {}
> -
> -#endif
> -
>   static void poison_obj(struct kmem_cache *cachep, void *addr, unsigned char val)
>   {
>   	int size = cachep->object_size;
> @@ -2062,7 +2060,7 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
>   
>   #if DEBUG
>   	/*
> -	 * If we're going to use the generic kernel_map_pages()
> +	 * If we're going to use the generic debug_pagealloc_map_pages()
>   	 * poisoning, then it's going to smash the contents of
>   	 * the redzone and userword anyhow, so switch them off.
>   	 */