[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>

2 files changed, 43 insertions, 11 deletions

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 14610b56c132..2a2153ebfe0b 100644
--- a/include/linux/gfp.h
+++ b/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
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index adae3c915938..76d33e688593 100644
--- a/include/linux/mmzone.h
+++ b/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)