[PATCH] reduce MAX_NR_ZONES: make ZONE_DMA32 optional

Make ZONE_DMA32 optional

- Add #ifdefs around ZONE_DMA32 specific code and definitions.

- Add CONFIG_ZONE_DMA32 config option and use that for x86_64
  that alone needs this zone.

- Remove the use of CONFIG_DMA_IS_DMA32 and CONFIG_DMA_IS_NORMAL
  for ia64 and fix up the way per node ZVCs are calculated.

- Fall back to prior GFP_ZONEMASK of 0x03 if there is no
  DMA32 zone.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ia64/Kconfig

@@ -66,15 +66,6 @@ config IA64_UNCACHED_ALLOCATOR
 	bool
 	select GENERIC_ALLOCATOR
 
-config DMA_IS_DMA32
-	bool
-	default y
-
-config DMA_IS_NORMAL
-	bool
-	depends on IA64_SGI_SN2
-	default y
-
 config AUDIT_ARCH
 	bool
 	default y

arch/x86_64/Kconfig

@@ -24,6 +24,10 @@ config X86
 	bool
 	default y
 
+config ZONE_DMA32
+	bool
+	default y
+
 config LOCKDEP_SUPPORT
 	bool
 	default y

include/linux/gfp.h

@@ -13,7 +13,7 @@ struct vm_area_struct;
 /* Zone modifiers in GFP_ZONEMASK (see linux/mmzone.h - low three bits) */
 #define __GFP_DMA	((__force gfp_t)0x01u)
 #define __GFP_HIGHMEM	((__force gfp_t)0x02u)
-#ifdef CONFIG_DMA_IS_DMA32
+#ifndef CONFIG_ZONE_DMA32
 #define __GFP_DMA32	((__force gfp_t)0x01)	/* ZONE_DMA is ZONE_DMA32 */
 #elif BITS_PER_LONG < 64
 #define __GFP_DMA32	((__force gfp_t)0x00)	/* ZONE_NORMAL is ZONE_DMA32 */

include/linux/mmzone.h

@@ -109,12 +109,14 @@ enum zone_type {
 	 * 			<16M.
 	 */
 	ZONE_DMA,
+#ifdef CONFIG_ZONE_DMA32
 	/*
 	 * x86_64 needs two ZONE_DMAs because it supports devices that are
 	 * only able to do DMA to the lower 16M but also 32 bit devices that
 	 * can only do DMA areas below 4G.
 	 */
 	ZONE_DMA32,
+#endif
 	/*
 	 * Normal addressable memory is in ZONE_NORMAL. DMA operations can be
 	 * performed on pages in ZONE_NORMAL if the DMA devices support
@@ -161,10 +163,14 @@ enum zone_type {
  *
  * NOTE! Make sure this matches the zones in <linux/gfp.h>
  */
-#define GFP_ZONEMASK	0x07
-/* #define GFP_ZONETYPES       (GFP_ZONEMASK + 1) */           /* Non-loner */
 #define GFP_ZONETYPES		((GFP_ZONEMASK + 1) / 2 + 1)    /* Loner */
 
+#ifdef CONFIG_ZONE_DMA32
+#define GFP_ZONEMASK		0x07
+#else
+#define GFP_ZONEMASK		0x03
+#endif
+
 struct zone {
 	/* Fields commonly accessed by the page allocator */
 	unsigned long		free_pages;
@@ -429,7 +435,11 @@ static inline int is_normal(struct zone *zone)
 
 static inline int is_dma32(struct zone *zone)
 {
+#ifdef CONFIG_ZONE_DMA32
 	return zone == zone->zone_pgdat->node_zones + ZONE_DMA32;
+#else
+	return 0;
+#endif
 }
 
 static inline int is_dma(struct zone *zone)

include/linux/vmstat.h

@@ -124,12 +124,10 @@ static inline unsigned long node_page_state(int node,
 	struct zone *zones = NODE_DATA(node)->node_zones;
 
 	return
-#ifndef CONFIG_DMA_IS_NORMAL
-#if !defined(CONFIG_DMA_IS_DMA32) && BITS_PER_LONG >= 64
+#ifdef CONFIG_ZONE_DMA32
 		zone_page_state(&zones[ZONE_DMA32], item) +
 #endif
 		zone_page_state(&zones[ZONE_NORMAL], item) +
-#endif
 #ifdef CONFIG_HIGHMEM
 		zone_page_state(&zones[ZONE_HIGHMEM], item) +
 #endif

mm/page_alloc.c

@@ -70,7 +70,9 @@ static void __free_pages_ok(struct page *page, unsigned int order);
  */
 int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = {
 	 256,
+#ifdef CONFIG_ZONE_DMA32
 	 256,
+#endif
 	 32
 };
 
@@ -85,7 +87,9 @@ EXPORT_SYMBOL(zone_table);
 
 static char *zone_names[MAX_NR_ZONES] = {
 	 "DMA",
+#ifdef CONFIG_ZONE_DMA32
 	 "DMA32",
+#endif
 	 "Normal",
 	 "HighMem"
 };
@@ -1373,8 +1377,10 @@ static inline int highest_zone(int zone_bits)
 	int res = ZONE_NORMAL;
 	if (zone_bits & (__force int)__GFP_HIGHMEM)
 		res = ZONE_HIGHMEM;
+#ifdef CONFIG_ZONE_DMA32
 	if (zone_bits & (__force int)__GFP_DMA32)
 		res = ZONE_DMA32;
+#endif
 	if (zone_bits & (__force int)__GFP_DMA)
 		res = ZONE_DMA;
 	return res;