From: Christoph Lameter <clameter@sgi.com>

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.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 include/linux/gfp.h    |    6 ++++++
 include/linux/mmzone.h |   19 +++++++++++++++++--
 mm/page_alloc.c        |    6 ++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff -puN include/linux/gfp.h~reduce-max_nr_zones-make-zone_highmem-optional include/linux/gfp.h
--- a/include/linux/gfp.h~reduce-max_nr_zones-make-zone_highmem-optional
+++ a/include/linux/gfp.h
@@ -12,7 +12,13 @@ struct vm_area_struct;
  */
 /* Zone modifiers in GFP_ZONEMASK (see linux/mmzone.h - low three bits) */
 #define __GFP_DMA	((__force gfp_t)0x01u)
+
+#ifdef CONFIG_HIGHMEM
 #define __GFP_HIGHMEM	((__force gfp_t)0x02u)
+#else
+#define __GFP_HIGHMEM	((__force gfp_t)0x00)	/* NORMAL is HIGHMEM */
+#endif
+
 #ifndef CONFIG_ZONE_DMA32
 #define __GFP_DMA32	((__force gfp_t)0x01)	/* ZONE_DMA is ZONE_DMA32 */
 #elif BITS_PER_LONG < 64
diff -puN include/linux/mmzone.h~reduce-max_nr_zones-make-zone_highmem-optional include/linux/mmzone.h
--- a/include/linux/mmzone.h~reduce-max_nr_zones-make-zone_highmem-optional
+++ a/include/linux/mmzone.h
@@ -122,6 +122,7 @@ 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
@@ -131,11 +132,10 @@ 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
@@ -166,8 +166,15 @@ enum zone_type {
 
 #ifdef CONFIG_ZONE_DMA32
 #define GFP_ZONEMASK		0x07
+#define	ZONES_SHIFT		2	/* ceil(log2(MAX_NR_ZONES)) */
 #else
+#ifdef CONFIG_HIGHMEM
 #define GFP_ZONEMASK		0x03
+#define	ZONES_SHIFT		2
+#else
+#define GFP_ZONEMASK		0x01
+#define ZONES_SHIFT		1
+#endif
 #endif
 
 struct zone {
@@ -408,7 +415,11 @@ static inline int populated_zone(struct 
 
 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)
@@ -424,7 +435,11 @@ static inline int is_normal_idx(enum zon
  */
 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)
diff -puN mm/page_alloc.c~reduce-max_nr_zones-make-zone_highmem-optional mm/page_alloc.c
--- a/mm/page_alloc.c~reduce-max_nr_zones-make-zone_highmem-optional
+++ a/mm/page_alloc.c
@@ -73,7 +73,9 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_Z
 #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_nod
 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;
_