Re: [PATCH v2 04/10] power: separate PageHighMem() and PageHighMemZone() use case

[Christoph Hellwig]

On Wed, Apr 29, 2020 at 12:26:37PM +0900, js1304@xxxxxxxxx wrote:
> index 6598001..be759a6 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -1227,7 +1227,7 @@ static struct page *saveable_highmem_page(struct zone *zone, unsigned long pfn)
>  	if (!page || page_zone(page) != zone)
>  		return NULL;
>  
> -	BUG_ON(!PageHighMem(page));
> +	BUG_ON(!PageHighMemZone(page));

The above check already checks for the highmem zone.  So if we want
to keep the BUG_ON it needs stay PageHighMem to make sense.  That being
said I'd rather remove it entirelá.

> -	BUG_ON(PageHighMem(page));
> +	BUG_ON(PageHighMemZone(page));

Same here.

> @@ -1529,7 +1529,7 @@ static unsigned long preallocate_image_pages(unsigned long nr_pages, gfp_t mask)
>  		if (!page)
>  			break;
>  		memory_bm_set_bit(&copy_bm, page_to_pfn(page));
> -		if (PageHighMem(page))
> +		if (PageHighMemZone(page))
>  			alloc_highmem++;
>  		else
>  			alloc_normal++;

I don't fully understand the log here.  Can Pavel or Rafael clarify
why swsupst would care about the exact zone?