diff -urN linux-2.4.17-rc2-virgin/include/asm-i386/pgtable.h linux-2.4.17-rc2/include/asm-i386/pgtable.h
--- linux-2.4.17-rc2-virgin/include/asm-i386/pgtable.h	Thu Nov 22 11:46:19 2001
+++ linux-2.4.17-rc2/include/asm-i386/pgtable.h	Tue Dec 18 21:31:40 2001
@@ -267,7 +267,18 @@
  * Permanent address of a page. Obviously must never be
  * called on a highmem page.
  */
+#ifndef CONFIG_HIGHMEM
+
+#define page_address(page)						\
+	__va( (((page) - PageZone(page)->zone_mem_map) << PAGE_SHIFT)	\
+			+ PageZone(page)->zone_start_paddr)
+
+#else /* CONFIG_HIGHMEM */
+
 #define page_address(page) ((page)->virtual)
+
+#endif /* CONFIG_HIGHMEM */
+
 #define pages_to_mb(x) ((x) >> (20-PAGE_SHIFT))
 
 /*
diff -urN linux-2.4.17-rc2-virgin/include/linux/mm.h linux-2.4.17-rc2/include/linux/mm.h
--- linux-2.4.17-rc2-virgin/include/linux/mm.h	Tue Dec 18 21:21:56 2001
+++ linux-2.4.17-rc2/include/linux/mm.h	Tue Dec 18 21:45:25 2001
@@ -162,9 +162,20 @@
 	wait_queue_head_t wait;		/* Page locked?  Stand in line... */
 	struct page **pprev_hash;	/* Complement to *next_hash. */
 	struct buffer_head * buffers;	/* Buffer maps us to a disk block. */
+
+
+	/*
+	 * On ordinary machines the direct mapped kernel virtual address
+	 * space allows kernel virtual addresses for given pages to be
+	 * computed by address calculation. On machines where kernel
+	 * virtual mapping for some regions of physical memory is done
+	 * dynamically the only way to deduce the kernel virtual address
+	 * of a physical page is by storing it somewhere, namely here.
+	 */
+#ifdef CONFIG_HIGHMEM
 	void *virtual;			/* Kernel virtual address (NULL if
 					   not kmapped, ie. highmem) */
-	struct zone_struct *zone;	/* Memory zone we are in. */
+#endif /* CONFIG_HIGHMEM */
 } mem_map_t;
 
 /*
@@ -286,6 +297,15 @@
 #define PG_reserved		14
 #define PG_launder		15	/* written out by VM pressure.. */
 
+/*
+ * PG_zone is actually a two-bit bitfield starting at bit 16 of the
+ * ->flags component of struct page.
+ * PG_zonemask is used to extract only those relevant bits of the word
+ * in order to help extract the PG_zone field of ->flags.
+ */
+#define PG_zone			16
+#define PG_zonemask		(0x3UL << PG_zone)
+
 /* Make it prettier to test the above... */
 #define UnlockPage(page)	unlock_page(page)
 #define Page_Uptodate(page)	test_bit(PG_uptodate, &(page)->flags)
@@ -302,6 +322,40 @@
 #define PageLaunder(page)	test_bit(PG_launder, &(page)->flags)
 #define SetPageLaunder(page)	set_bit(PG_launder, &(page)->flags)
 
+/*
+ * The zone field within ->flags is never updated after free_area_init_core()
+ * sets it, so none of the operations on it need be atomic.
+ */
+#define PageZone(page)	\
+	(zone_table[(((page)->flags & PG_zonemask) >> PG_zone)])
+#define SetPageZone(page, zone_number)					\
+	do {								\
+		(page)->flags &= ~PG_zonemask;				\
+		(page)->flags |= (zone_number << PG_zone) & PG_zonemask;\
+	} while(0)
+
+/*
+ * In order to avoid #ifdefs within C code itself, a CONFIG_HIGHMEM
+ * conditional macro to access the ->virtual field of struct page is
+ * provided here.
+ */
+#ifdef CONFIG_HIGHMEM
+
+#define SetPageVirtual(page, address)		\
+	do {					\
+		(page)->virtual = (address);	\
+	} while(0)
+
+#else /* !CONFIG_HIGHMEM */
+
+/*
+ * With no highmem, there is no field to be set, and so
+ * this expands to a no-op.
+ */
+#define SetPageVirtual(page, address)	do { ; } while(0)
+
+#endif /* !CONFIG_HIGHMEM */
+
 extern void FASTCALL(set_page_dirty(struct page *));
 
 /*
@@ -448,6 +502,9 @@
 extern void show_mem(void);
 extern void si_meminfo(struct sysinfo * val);
 extern void swapin_readahead(swp_entry_t);
+
+struct zone_struct;
+extern struct zone_struct *zone_table[];
 
 extern struct address_space swapper_space;
 #define PageSwapCache(page) ((page)->mapping == &swapper_space)
diff -urN linux-2.4.17-rc2-virgin/mm/Makefile linux-2.4.17-rc2/mm/Makefile
--- linux-2.4.17-rc2-virgin/mm/Makefile	Wed Oct 24 15:21:18 2001
+++ linux-2.4.17-rc2/mm/Makefile	Tue Dec 18 21:12:43 2001
@@ -9,7 +9,7 @@
 
 O_TARGET := mm.o
 
-export-objs := shmem.o filemap.o
+export-objs := shmem.o filemap.o page_alloc.o
 
 obj-y	 := memory.o mmap.o filemap.o mprotect.o mlock.o mremap.o \
 	    vmalloc.o slab.o bootmem.o swap.o vmscan.o page_io.o \
diff -urN linux-2.4.17-rc2-virgin/mm/page_alloc.c linux-2.4.17-rc2/mm/page_alloc.c
--- linux-2.4.17-rc2-virgin/mm/page_alloc.c	Mon Nov 19 16:35:40 2001
+++ linux-2.4.17-rc2/mm/page_alloc.c	Tue Dec 18 21:44:55 2001
@@ -18,6 +18,7 @@
 #include <linux/bootmem.h>
 #include <linux/slab.h>
 #include <linux/compiler.h>
+#include <linux/module.h>
 
 int nr_swap_pages;
 int nr_active_pages;
@@ -26,6 +27,17 @@
 struct list_head active_list;
 pg_data_t *pgdat_list;
 
+
+/*
+ * The zone_table array is used to look up the address of the
+ * struct zone corresponding to a given zone number (ZONE_DMA,
+ * ZONE_NORMAL, or ZONE_HIGHMEM). Specifically, struct page uses
+ * a bitfield within ->flags to store the zone to which a page
+ * belongs, and so lookups to this tabl are essential.
+ */
+zone_t *zone_table[MAX_NR_ZONES];
+EXPORT_SYMBOL(zone_table);
+
 static char *zone_names[MAX_NR_ZONES] = { "DMA", "Normal", "HighMem" };
 static int zone_balance_ratio[MAX_NR_ZONES] __initdata = { 128, 128, 128, };
 static int zone_balance_min[MAX_NR_ZONES] __initdata = { 20 , 20, 20, };
@@ -54,7 +66,12 @@
 /*
  * Temporary debugging check.
  */
-#define BAD_RANGE(zone,x) (((zone) != (x)->zone) || (((x)-mem_map) < (zone)->zone_start_mapnr) || (((x)-mem_map) >= (zone)->zone_start_mapnr+(zone)->size))
+#define BAD_RANGE(zone, page)						\
+(									\
+	(((page) - mem_map) >= ((zone)->zone_start_mapnr+(zone)->size))	\
+	|| (((page) - mem_map) < (zone)->zone_start_mapnr)		\
+	|| ((zone) != PageZone(page))					\
+)
 
 /*
  * Buddy system. Hairy. You really aren't expected to understand this
@@ -90,7 +107,7 @@
 		goto local_freelist;
  back_local_freelist:
 
-	zone = page->zone;
+	zone = PageZone(page);
 
 	mask = (~0UL) << order;
 	base = zone->zone_mem_map;
@@ -255,7 +272,7 @@
 			entry = local_pages->next;
 			do {
 				tmp = list_entry(entry, struct page, list);
-				if (tmp->index == order && memclass(tmp->zone, classzone)) {
+				if (tmp->index == order && memclass(PageZone(tmp), classzone)) {
 					list_del(entry);
 					current->nr_local_pages--;
 					set_page_count(tmp, 1);
@@ -699,6 +716,7 @@
 		unsigned long mask;
 		unsigned long size, realsize;
 
+		zone_table[j] = zone;
 		realsize = size = zones_size[j];
 		if (zholes_size)
 			realsize -= zholes_size[j];
@@ -733,9 +751,10 @@
 
 		for (i = 0; i < size; i++) {
 			struct page *page = mem_map + offset + i;
-			page->zone = zone;
+			SetPageZone(page, j);
+
 			if (j != ZONE_HIGHMEM)
-				page->virtual = __va(zone_start_paddr);
+				SetPageVirtual(page, __va(zone_start_paddr));
 			zone_start_paddr += PAGE_SIZE;
 		}
 
diff -urN linux-2.4.17-rc2-virgin/mm/vmscan.c linux-2.4.17-rc2/mm/vmscan.c
--- linux-2.4.17-rc2-virgin/mm/vmscan.c	Tue Dec 18 21:21:57 2001
+++ linux-2.4.17-rc2/mm/vmscan.c	Tue Dec 18 21:22:38 2001
@@ -58,7 +58,7 @@
 		return 0;
 
 	/* Don't bother replenishing zones not under pressure.. */
-	if (!memclass(page->zone, classzone))
+	if (!memclass(PageZone(page), classzone))
 		return 0;
 
 	if (TryLockPage(page))
@@ -369,7 +369,7 @@
 		if (unlikely(!page_count(page)))
 			continue;
 
-		if (!memclass(page->zone, classzone))
+		if (!memclass(PageZone(page), classzone))
 			continue;
 
 		/* Racy check to avoid trylocking when not worthwhile */