Re: [RFC] [PATCH] virtual memmap on sparsemem v3 [3/4] static virtual mem_map

[Andrew Morton <akpm@osdl.org>]

On Fri, 8 Dec 2006 16:07:08 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> This patch adds support for statically allocated virtual mem_map.
> (means virtual address of mem_map array is defined statically.)
> This removes reference to *(&mem_map).
> 
> Signed-Off-By: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> 
> Index: devel-2.6.19/include/linux/mmzone.h
> ===================================================================
> --- devel-2.6.19.orig/include/linux/mmzone.h	2006-12-08 15:04:30.000000000 +0900
> +++ devel-2.6.19/include/linux/mmzone.h	2006-12-08 15:05:18.000000000 +0900
> @@ -618,8 +618,13 @@
>  #if (((BITS_PER_LONG/4) * PAGES_PER_SECTION) % PAGE_SIZE) != 0
>  #error "PAGE_SIZE/SECTION_SIZE relationship is not suitable for vmem_map"
>  #endif
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP_STATIC
> +#include <linux/mm_types.h>
> +extern struct page mem_map[];
> +#else
>  extern struct page* mem_map;
>  #endif
> +#endif

This looks rather unpleasant - what went wrong here?

Would prefer to unconditionally include the header file - conditional inclusions
like this can cause compile failures when someone changes a config option.  They
generally raise the complexity level.