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Date: Fri, 29 Feb 2008 20:05:41 -0800
From: Christoph Lameter <clameter@....com>
To: linux-kernel@...r.kernel.org
Subject: [rfc 07/10] 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@....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 2008-02-29 19:21:35.000000000 -0800
+++ linux-2.6/include/linux/mm.h 2008-02-29 19:29:53.000000000 -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
#define NODES_WIDTH 0
@@ -447,8 +447,8 @@ 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 2008-02-29 19:13:55.000000000 -0800
+++ linux-2.6/include/linux/mmzone.h 2008-02-29 19:29:53.000000000 -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 2008-02-29 19:20:11.000000000 -0800
+++ linux-2.6/include/linux/page-flags.h 2008-02-29 19:29:53.000000000 -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. */
@@ -86,7 +86,6 @@ enum pageflags {
PG_mappedtodisk, /* Has blocks allocated on-disk */
PG_reclaim, /* To be reclaimed asap */
PG_buddy, /* Page is free, on buddy lists */
- NR_PAGEFLAGS, /* For verification purposes */
#if (BITS_PER_LONG > 32)
/*
@@ -98,6 +97,7 @@ enum pageflags {
*/
PG_uncached = 31, /* Page has been mapped as uncached */
#endif
+ __NR_PAGEFLAGS,
};
/*
Index: linux-2.6/kernel/bounds.c
===================================================================
--- linux-2.6.orig/kernel/bounds.c 2008-02-29 19:29:38.000000000 -0800
+++ linux-2.6/kernel/bounds.c 2008-02-29 19:29:53.000000000 -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 2008-02-29 19:30:04.000000000 -0800
+++ linux-2.6/include/linux/bounds.h 2008-02-29 19:30:08.000000000 -0800
@@ -7,4 +7,6 @@
*
*/
+#define NR_PAGEFLAGS 32 /* __NR_PAGEFLAGS # */
+
#endif
--
--
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