3 files changed, 52 insertions, 22 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1813b162b0a8..57b2ead51dba 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -395,19 +395,41 @@ static inline void put_page(struct page *page)
 /*
  * The zone field is never updated after free_area_init_core()
  * sets it, so none of the operations on it need to be atomic.
- * We'll have up to (MAX_NUMNODES * MAX_NR_ZONES) zones total,
- * so we use (MAX_NODES_SHIFT + MAX_ZONES_SHIFT) here to get enough bits.
  */
-#define NODEZONE_SHIFT (sizeof(page_flags_t)*8 - MAX_NODES_SHIFT - MAX_ZONES_SHIFT)
+
+/* Page flags: | NODE | ZONE | ... | FLAGS | */
+#define NODES_PGOFF             ((sizeof(page_flags_t)*8) - NODES_SHIFT)
+#define ZONES_PGOFF             (NODES_PGOFF - ZONES_SHIFT)
+
+/*
+ * Define the bit shifts to access each section.  For non-existant
+ * sections we define the shift as 0; that plus a 0 mask ensures
+ * the compiler will optimise away reference to them.
+ */
+#define NODES_PGSHIFT           (NODES_PGOFF * (NODES_SHIFT != 0))
+#define ZONES_PGSHIFT           (ZONES_PGOFF * (ZONES_SHIFT != 0))
+
+/* NODE:ZONE is used to lookup the zone from a page. */
+#define ZONETABLE_SHIFT         (NODES_SHIFT + ZONES_SHIFT)
+#define ZONETABLE_PGSHIFT       ZONES_PGSHIFT
+
+#if NODES_SHIFT+ZONES_SHIFT > FLAGS_RESERVED
+#error NODES_SHIFT+ZONES_SHIFT > FLAGS_RESERVED
+#endif
+
 #define NODEZONE(node, zone)    ((node << ZONES_SHIFT) | zone)
 
+#define ZONES_MASK              ((1UL << ZONES_SHIFT) - 1)
+#define NODES_MASK              ((1UL << NODES_SHIFT) - 1)
+#define ZONETABLE_MASK          ((1UL << ZONETABLE_SHIFT) - 1)
+
 static inline unsigned long page_zonenum(struct page *page)
 {
-        return (page->flags >> NODEZONE_SHIFT) & (~(~0UL << ZONES_SHIFT));
+        return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK;
 }
 static inline unsigned long page_to_nid(struct page *page)
 {
-        return (page->flags >> (NODEZONE_SHIFT + ZONES_SHIFT));
+        return (page->flags >> NODES_PGSHIFT) & NODES_MASK;
 }
 
 struct zone;
@@ -415,13 +437,26 @@ extern struct zone *zone_table[];
 
 static inline struct zone *page_zone(struct page *page)
 {
-        return zone_table[page->flags >> NODEZONE_SHIFT];
+        return zone_table[(page->flags >> ZONETABLE_PGSHIFT) &
+                        ZONETABLE_MASK];
+}
+
+static inline void set_page_zone(struct page *page, unsigned long zone)
+{
+        page->flags &= ~(ZONES_MASK << ZONES_PGSHIFT);
+        page->flags |= (zone & ZONES_MASK) << ZONES_PGSHIFT;
+}
+static inline void set_page_node(struct page *page, unsigned long node)
+{
+        page->flags &= ~(NODES_MASK << NODES_PGSHIFT);
+        page->flags |= (node & NODES_MASK) << NODES_PGSHIFT;
 }
 
-static inline void set_page_zone(struct page *page, unsigned long nodezone_num)
+static inline void set_page_links(struct page *page, unsigned long zone,
+        unsigned long node)
 {
-        page->flags &= ~(~0UL << NODEZONE_SHIFT);
-        page->flags |= nodezone_num << NODEZONE_SHIFT;
+        set_page_zone(page, zone);
+        set_page_node(page, node);
 }
 
 #ifndef CONFIG_DISCONTIGMEM
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index b79633d3a97b..39e912708e2a 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -414,30 +414,25 @@ extern struct pglist_data contig_page_data;
 
 #include <asm/mmzone.h>
 
+#endif /* !CONFIG_DISCONTIGMEM */
+
 #if BITS_PER_LONG == 32 || defined(ARCH_HAS_ATOMIC_UNSIGNED)
 /*
  * with 32 bit page->flags field, we reserve 8 bits for node/zone info.
  * there are 3 zones (2 bits) and this leaves 8-2=6 bits for nodes.
  */
-#define MAX_NODES_SHIFT         6
+#define FLAGS_RESERVED          8
+
 #elif BITS_PER_LONG == 64
 /*
  * with 64 bit flags field, there's plenty of room.
  */
-#define MAX_NODES_SHIFT         10
-#endif
+#define FLAGS_RESERVED          32
 
-#endif /* !CONFIG_DISCONTIGMEM */
-
-#if NODES_SHIFT > MAX_NODES_SHIFT
-#error NODES_SHIFT > MAX_NODES_SHIFT
-#endif
+#else
 
-/* There are currently 3 zones: DMA, Normal & Highmem, thus we need 2 bits */
-#define MAX_ZONES_SHIFT         2
+#error BITS_PER_LONG not defined
 
-#if ZONES_SHIFT > MAX_ZONES_SHIFT
-#error ZONES_SHIFT > MAX_ZONES_SHIFT
 #endif
 
 #endif /* !__ASSEMBLY__ */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bf1dd8819097..1958358e29b0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1653,7 +1653,7 @@ void __init memmap_init_zone(unsigned long size, int nid, unsigned long zone,
         struct page *page;
 
         for (page = start; page < (start + size); page++) {
-                set_page_zone(page, NODEZONE(nid, zone));
+                set_page_links(page, zone, nid);
                 set_page_count(page, 0);
                 reset_page_mapcount(page);
                 SetPageReserved(page);