From: Christoph Lameter <clameter@sgi.com>
Subject: Pageflags: Get rid of FLAGS_RESERVED

NR_PAGEFLAGS specifies the number of page flags we are using.
From that we can calculate the number of bits leftover that can
be used for zone, node (and maybe the sections id). There is
no need anymore for FLAGS_RESERVED if we use NR_PAGEFLAGS.

Use the new methods to make NR_PAGEFLAGS available via
the preprocessor. NR_PAGEFLAGS is used to calculate field
boundaries in the page flags fields. These field widths have
to be available to the preprocessor.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 include/linux/bounds.h     |    2 ++
 include/linux/mm.h         |    6 +++---
 include/linux/mmzone.h     |   19 -------------------
 include/linux/page-flags.h |   14 +++++++-------
 kernel/bounds.c            |    1 +
 5 files changed, 13 insertions(+), 29 deletions(-)

Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h	2008-03-03 14:59:44.321594074 -0800
+++ linux-2.6/include/linux/mm.h	2008-03-03 14:59:54.897780018 -0800
@@ -402,7 +402,7 @@ static inline void set_compound_order(st
 
 #define ZONES_WIDTH		ZONES_SHIFT
 
-#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= FLAGS_RESERVED
+#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
 #define NODES_WIDTH		NODES_SHIFT
 #else
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
@@ -450,8 +450,8 @@ static inline void set_compound_order(st
 
 #define ZONEID_PGSHIFT		(ZONEID_PGOFF * (ZONEID_SHIFT != 0))
 
-#if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH > FLAGS_RESERVED
-#error SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH > FLAGS_RESERVED
+#if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH > BITS_PER_LONG - NR_PAGEFLAGS
+#error SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH > BITS_PER_LONG - NR_PAGEFLAGS
 #endif
 
 #define ZONES_MASK		((1UL << ZONES_WIDTH) - 1)
Index: linux-2.6/include/linux/mmzone.h
===================================================================
--- linux-2.6.orig/include/linux/mmzone.h	2008-03-03 14:59:05.644918630 -0800
+++ linux-2.6/include/linux/mmzone.h	2008-03-03 14:59:54.897780018 -0800
@@ -735,25 +735,6 @@ extern struct zone *next_zone(struct zon
 #include <asm/sparsemem.h>
 #endif
 
-#if BITS_PER_LONG == 32
-/*
- * with 32 bit page->flags field, we reserve 9 bits for node/zone info.
- * there are 4 zones (3 bits) and this leaves 9-3=6 bits for nodes.
- */
-#define FLAGS_RESERVED		9
-
-#elif BITS_PER_LONG == 64
-/*
- * with 64 bit flags field, there's plenty of room.
- */
-#define FLAGS_RESERVED		32
-
-#else
-
-#error BITS_PER_LONG not defined
-
-#endif
-
 #if !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) && \
 	!defined(CONFIG_ARCH_POPULATES_NODE_MAP)
 #define early_pfn_to_nid(nid)  (0UL)
Index: linux-2.6/include/linux/page-flags.h
===================================================================
--- linux-2.6.orig/include/linux/page-flags.h	2008-03-03 14:59:40.217522522 -0800
+++ linux-2.6/include/linux/page-flags.h	2008-03-03 15:00:12.294099465 -0800
@@ -7,6 +7,7 @@
 
 #include <linux/types.h>
 #include <linux/mm_types.h>
+#include <linux/bounds.h>
 
 /*
  * Various page->flags bits:
@@ -59,13 +60,12 @@
  * extends from the high bits downwards.
  *
  *  | FIELD | ... | FLAGS |
- *  N-1     ^             0
- *          (N-FLAGS_RESERVED)
+ *  N-1           ^       0
+ *               (NR_PAGEFLAGS)
  *
- * The fields area is reserved for fields mapping zone, node and SPARSEMEM
- * section.  The boundry between these two areas is defined by
- * FLAGS_RESERVED which defines the width of the fields section
- * (see linux/mmzone.h).  New flags must _not_ overlap with this area.
+ * The fields area is reserved for fields mapping zone, node (for NUMA) and
+ * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
+ * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
  */
 enum pageflags {
 	PG_locked,		/* Page is locked. Don't touch. */
@@ -97,7 +97,7 @@ enum pageflags {
  */
 	PG_uncached = 31,		/* Page has been mapped as uncached */
 #endif
-	NR_PAGEFLAGS
+	__NR_PAGEFLAGS
 };
 
 /*
Index: linux-2.6/kernel/bounds.c
===================================================================
--- linux-2.6.orig/kernel/bounds.c	2008-03-03 14:59:46.637634511 -0800
+++ linux-2.6/kernel/bounds.c	2008-03-03 14:59:54.901779835 -0800
@@ -13,4 +13,5 @@
 
 void foo(void)
 {
+	DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
 }
Index: linux-2.6/include/linux/bounds.h
===================================================================
--- linux-2.6.orig/include/linux/bounds.h	2008-03-03 14:59:46.637634511 -0800
+++ linux-2.6/include/linux/bounds.h	2008-03-03 14:59:54.901779835 -0800
@@ -7,4 +7,6 @@
  *
  */
 
+#define NR_PAGEFLAGS 32 /* __NR_PAGEFLAGS	# */
+
 #endif