[PATCH] reduce MAX_NR_ZONES: make ZONE_HIGHMEM optional

Make ZONE_HIGHMEM optional

- ifdef out code and definitions related to CONFIG_HIGHMEM

- __GFP_HIGHMEM falls back to normal allocations if there is no
  ZONE_HIGHMEM

- GFP_ZONEMASK becomes 0x01 if there is no DMA32 and no HIGHMEM
  zone.

[jdike@addtoit.com: build fix]
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/kernel/mem.c

@@ -226,7 +226,9 @@ void paging_init(void)
 	for(i=0;i<sizeof(zones_size)/sizeof(zones_size[0]);i++) 
 		zones_size[i] = 0;
 	zones_size[ZONE_DMA] = (end_iomem >> PAGE_SHIFT) - (uml_physmem >> PAGE_SHIFT);
+#ifdef CONFIG_HIGHMEM
 	zones_size[ZONE_HIGHMEM] = highmem >> PAGE_SHIFT;
+#endif
 	free_area_init(zones_size);
 
 	/*

include/linux/gfp.h

@@ -9,17 +9,19 @@ struct vm_area_struct;
 
 /*
  * GFP bitmasks..
+ *
+ * Zone modifiers (see linux/mmzone.h - low three bits)
+ *
+ * These may be masked by GFP_ZONEMASK to make allocations with this bit
+ * set fall back to ZONE_NORMAL.
+ *
+ * Do not put any conditional on these. If necessary modify the definitions
+ * without the underscores and use the consistently. The definitions here may
+ * be used in bit comparisons.
  */
-/* 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)
-#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 */
-#else
-#define __GFP_DMA32	((__force gfp_t)0x04)	/* Has own ZONE_DMA32 */
-#endif
+#define __GFP_DMA32	((__force gfp_t)0x04u)
 
 /*
  * Action modifiers - doesn't change the zoning

include/linux/mmzone.h

@@ -123,6 +123,7 @@ enum zone_type {
 	 * transfers to all addressable memory.
 	 */
 	ZONE_NORMAL,
+#ifdef CONFIG_HIGHMEM
 	/*
 	 * A memory area that is only addressable by the kernel through
 	 * mapping portions into its own address space. This is for example
@@ -132,11 +133,10 @@ enum zone_type {
 	 * access.
 	 */
 	ZONE_HIGHMEM,
-
+#endif
 	MAX_NR_ZONES
 };
 
-#define	ZONES_SHIFT		2	/* ceil(log2(MAX_NR_ZONES)) */
 
 /*
  * When a memory allocation must conform to specific limitations (such
@@ -163,12 +163,34 @@ enum zone_type {
  *
  * NOTE! Make sure this matches the zones in <linux/gfp.h>
  */
-#define GFP_ZONETYPES		((GFP_ZONEMASK + 1) / 2 + 1)    /* Loner */
 
 #ifdef CONFIG_ZONE_DMA32
+
+#ifdef CONFIG_HIGHMEM
+#define GFP_ZONETYPES		((GFP_ZONEMASK + 1) / 2 + 1)    /* Loner */
 #define GFP_ZONEMASK		0x07
+#define ZONES_SHIFT		2	/* ceil(log2(MAX_NR_ZONES)) */
 #else
+#define GFP_ZONETYPES		((0x07 + 1) / 2 + 1)    /* Loner */
+/* Mask __GFP_HIGHMEM */
+#define GFP_ZONEMASK		0x05
+#define ZONES_SHIFT		2
+#endif
+
+#else
+#ifdef CONFIG_HIGHMEM
+
 #define GFP_ZONEMASK		0x03
+#define ZONES_SHIFT		2
+#define GFP_ZONETYPES		3
+
+#else
+
+#define GFP_ZONEMASK		0x01
+#define ZONES_SHIFT		1
+#define GFP_ZONETYPES		2
+
+#endif
 #endif
 
 struct zone {
@@ -409,7 +431,11 @@ static inline int populated_zone(struct zone *zone)
 
 static inline int is_highmem_idx(enum zone_type idx)
 {
+#ifdef CONFIG_HIGHMEM
 	return (idx == ZONE_HIGHMEM);
+#else
+	return 0;
+#endif
 }
 
 static inline int is_normal_idx(enum zone_type idx)
@@ -425,7 +451,11 @@ static inline int is_normal_idx(enum zone_type idx)
  */
 static inline int is_highmem(struct zone *zone)
 {
+#ifdef CONFIG_HIGHMEM
 	return zone == zone->zone_pgdat->node_zones + ZONE_HIGHMEM;
+#else
+	return 0;
+#endif
 }
 
 static inline int is_normal(struct zone *zone)

mm/page_alloc.c

@@ -73,7 +73,9 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = {
 #ifdef CONFIG_ZONE_DMA32
 	 256,
 #endif
+#ifdef CONFIG_HIGHMEM
 	 32
+#endif
 };
 
 EXPORT_SYMBOL(totalram_pages);
@@ -91,7 +93,9 @@ static char *zone_names[MAX_NR_ZONES] = {
 	 "DMA32",
 #endif
 	 "Normal",
+#ifdef CONFIG_HIGHMEM
 	 "HighMem"
+#endif
 };
 
 int min_free_kbytes = 1024;
@@ -1375,8 +1379,10 @@ static int __meminit build_zonelists_node(pg_data_t *pgdat,
 static inline int highest_zone(int zone_bits)
 {
 	int res = ZONE_NORMAL;
+#ifdef CONFIG_HIGHMEM
 	if (zone_bits & (__force int)__GFP_HIGHMEM)
 		res = ZONE_HIGHMEM;
+#endif
 #ifdef CONFIG_ZONE_DMA32
 	if (zone_bits & (__force int)__GFP_DMA32)
 		res = ZONE_DMA32;