remove zone_mem_map [1/4] remove zone_mem_map.

This patch removes zone->zone_mem_map.
Againt 2.6.16-rc1.

Because of SPARSEMEM's cleanup, there are no codes which touches zone->zone_mem_map directly.

My purpose is:
Reduce the assumptions of zones. Because of zone_mem_map, zone is considered to have contiguous mem_map. This patch removes that needless? assumption.
I'll try to remove zone_start_pfn etc.. if I can go ahead.

This patch affects many archs which has NUMA, so enough tests should be done. But I don't have test environments...
Please notify me if the kernel cannot be compiled or perfomance goes down because of this patch.
Sigh, binary modules which uses page_to_pfn() will not work either ;)

Index: hogehoge/include/linux/mmzone.h
===================================================================
@@ -212,7 +212,6 @@ struct zone {
 	 * Discontig memory support fields.
 	 */
 	struct pglist_data	*zone_pgdat;
-	struct page		*zone_mem_map;
 	/* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */
 	unsigned long		zone_start_pfn;
 

Index: hogehoge/mm/page_alloc.c
===================================================================
@@ -2009,7 +2009,6 @@ static __meminit void init_currently_emp
 	zone_wait_table_init(zone, size);
 	pgdat->nr_zones = zone_idx(zone) + 1;
 
-	zone->zone_mem_map = pfn_to_page(zone_start_pfn);
 	zone->zone_start_pfn = zone_start_pfn;
 
 	memmap_init(size, pgdat->node_id, zone_idx(zone), zone_start_pfn);

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