[PATCH] remove zone_mem_map

This patch removes zone_mem_map.

pfn_to_page uses pgdat, page_to_pfn uses zone.  page_to_pfn can use pgdat
instead of zone, which is only one user of zone_mem_map.  By modifing it,
we can remove zone_mem_map.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Christoph Lameter <christoph@lameter.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-alpha/mmzone.h

@@ -83,8 +83,7 @@ PLAT_NODE_DATA_LOCALNR(unsigned long p, int n)
 	pte_t pte;                                                           \
 	unsigned long pfn;                                                   \
 									     \
-	pfn = ((unsigned long)((page)-page_zone(page)->zone_mem_map)) << 32; \
-	pfn += page_zone(page)->zone_start_pfn << 32;			     \
+	pfn = page_to_pfn(page) << 32; \
 	pte_val(pte) = pfn | pgprot_val(pgprot);			     \
 									     \
 	pte;								     \

include/asm-generic/memory_model.h

@@ -45,11 +45,11 @@ extern unsigned long page_to_pfn(struct page *page);
 	NODE_DATA(__nid)->node_mem_map + arch_local_page_offset(__pfn, __nid);\
 })
 
-#define page_to_pfn(pg)			\
-({	struct page *__pg = (pg);		\
-	struct zone *__zone = page_zone(__pg);	\
-	(unsigned long)(__pg - __zone->zone_mem_map) +	\
-	 __zone->zone_start_pfn;			\
+#define page_to_pfn(pg)							\
+({	struct page *__pg = (pg);					\
+	struct pglist_data *__pgdat = NODE_DATA(page_to_nid(__pg));	\
+	(unsigned long)(__pg - __pgdat->node_mem_map) +			\
+	 __pgdat->node_start_pfn;					\
 })
 
 #elif defined(CONFIG_SPARSEMEM)

include/linux/mmzone.h

@@ -225,7 +225,6 @@ 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;
 

mm/page_alloc.c

@@ -2042,7 +2042,6 @@ static __meminit void init_currently_empty_zone(struct zone *zone,
 	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);
@@ -2768,9 +2767,8 @@ struct page *pfn_to_page(unsigned long pfn)
 }
 unsigned long page_to_pfn(struct page *page)
 {
-	struct zone *zone = page_zone(page);
-	return (page - zone->zone_mem_map) + zone->zone_start_pfn;
-
+	struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
+	return (page - pgdat->node_mem_map) + pgdat->node_start_pfn;
 }
 #elif defined(CONFIG_SPARSEMEM)
 struct page *pfn_to_page(unsigned long pfn)