Re: [RFC} memory unplug patchset prep [3/16] define is_identity_mapped

[David Rientjes <rientjes@google.com>]

On Tue, 6 Mar 2007, KAMEZAWA Hiroyuki wrote:

> Index: devel-tree-2.6.20-mm2/include/linux/mmzone.h
> ===================================================================
> --- devel-tree-2.6.20-mm2.orig/include/linux/mmzone.h
> +++ devel-tree-2.6.20-mm2/include/linux/mmzone.h
> @@ -523,6 +523,13 @@ static inline int is_normal_idx(enum zon
>  	return (idx == ZONE_NORMAL);
>  }
>  
> +static inline int is_identity_map_idx(enum zone_type idx)
> +{
> +	if (is_configured_zone(ZONE_HIGHMEM))
> +		return (idx < ZONE_HIGHMEM);
> +	else
> +		return 1;
> +}
>  /**
>   * is_highmem - helper function to quickly check if a struct zone is a 
>   *              highmem zone or not.  This is an attempt to keep references
> @@ -549,6 +556,14 @@ static inline int is_dma(struct zone *zo
>  	return zone == zone->zone_pgdat->node_zones + ZONE_DMA;
>  }
>  
> +static inline int is_identity_map(struct zone *zone)
> +{
> +	if (is_configured_zone(ZONE_HIGHMEM)
> +		return zone_idx(zone) < ZONE_HIGHMEM;
> +	else
> +		return 1;
> +}
> +

is_identity_map() isn't specific to any particular architecture nor is it 
dependent on a configuration option.  Since there's a missing ) in its 
conditional, I'm wondering how this entire patch was ever tested.

> Index: devel-tree-2.6.20-mm2/include/linux/page-flags.h
> ===================================================================
> --- devel-tree-2.6.20-mm2.orig/include/linux/page-flags.h
> +++ devel-tree-2.6.20-mm2/include/linux/page-flags.h
> @@ -162,7 +162,7 @@ static inline void SetPageUptodate(struc
>  #define __ClearPageSlab(page)	__clear_bit(PG_slab, &(page)->flags)
>  
>  #ifdef CONFIG_HIGHMEM
> -#define PageHighMem(page)	is_highmem(page_zone(page))
> +#define PageHighMem(page)	(!is_identitiy_map(page_zone(page)))
>  #else
>  #define PageHighMem(page)	0 /* needed to optimize away at compile time */
>  #endif

I assume this should be defined to !is_identity_map(page_zone(page)).

		David

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