[patch 1/2] own header file for struct page.

Heiko Carstens
2006-09-08T11:22:25Z

This moves the definition of struct page from mm.h to its own header file
page.h.
This is a prereq to fix SetPageUptodate which is broken on s390:

#define SetPageUptodate(_page)
do {
struct page *__page = (_page);
if (!test_and_set_bit(PG_uptodate, &__page->flags))
page_test_and_clear_dirty(_page);
} while (0)

_page gets used twice in this macro which can cause subtle bugs. Using
__page for the page_test_and_clear_dirty call doesn't work since it
causes yet another problem with the page_test_and_clear_dirty macro as
well.
In order to get of all these problems caused by macros it seems to
be a good idea to get rid of them and convert them to static inline
functions. Because of header file include order it's necessary to have a
seperate header file for the struct page definition.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
---

Patches are against git tree as of today. Better ideas welcome of course.

include/linux/mm.h | 64 --------------------------------------------
include/linux/page.h | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 75 insertions(+), 63 deletions(-)

Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h 2006-09-08 10:46:25.000000000 +0200
+++ linux-2.6/include/linux/mm.h 2006-09-08 12:41:49.000000000 +0200
@@ -15,6 +15,7 @@
#include <linux/fs.h>
#include <linux/mutex.h>
#include <linux/debug_locks.h>
+#include <linux/page.h>

struct mempolicy;
struct anon_vma;
@@ -215,64 +216,6 @@
struct inode;

/*
- * Each physical page in the system has a struct page associated with
- * it to keep track of whatever it is we are using the page for at the
- * moment. Note that we have no way to track which tasks are using
- * a page.
- */
-struct page {
- unsigned long flags; /* Atomic flags, some possibly
- * updated asynchronously */
- atomic_t _count; /* Usage count, see below. */
- atomic_t _mapcount; /* Count of ptes mapped in mms,
- * to show when page is mapped
- * & limit reverse map searches.
- */
- union {
- struct {
- unsigned long private; /* Mapping-private opaque data:
- * usually used for buffer_heads
- * if PagePrivate set; used for
- * swp_entry_t if PageSwapCache;
- * indicates order in the buddy
- * system if PG_buddy is set.
- */
- struct address_space *mapping; /* If low bit clear, points to
- * inode address_space, or NULL.
- * If page mapped as anonymous
- * memory, low bit is set, and
- * it points to anon_vma object:
- * see PAGE_MAPPING_ANON below.
- */
- };
-#if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
- spinlock_t ptl;
-#endif
- };
- pgoff_t index; /* Our offset within mapping. */
- struct list_head lru; /* Pageout list, eg. active_list
- * protected by zone->lru_lock !
- */
- /*
- * On machines where all RAM is mapped into kernel address space,
- * we can simply calculate the virtual address. On machines with
- * highmem some memory is mapped into kernel virtual memory
- * dynamically, so we need a place to store that address.
- * Note that this field could be 16 bits on x86 ... ;)
- *
- * Architectures with slow multiplication can define
- * WANT_PAGE_VIRTUAL in asm/page.h
- */
-#if defined(WANT_PAGE_VIRTUAL)
- void *virtual; /* Kernel virtual address (NULL if
- not kmapped, ie. highmem) */
-#endif /* WANT_PAGE_VIRTUAL */
-};
-
-#define page_private(page) ((page)->private)
-#define set_page_private(page, v) ((page)->private = (v))
-
-/*
* FIXME: take this include out, include page-flags.h in
* files which need it (119 of them)
*/
@@ -521,11 +464,6 @@
*/
#include <linux/vmstat.h>

-#ifndef CONFIG_DISCONTIGMEM
-/* The array of struct pages - for discontigmem use pgdat->lmem_map */
-extern struct page *mem_map;
-#endif
-
static __always_inline void *lowmem_page_address(struct page *page)
{
return __va(page_to_pfn(page) << PAGE_SHIFT);
Index: linux-2.6/include/linux/page.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/include/linux/page.h 2006-09-08 13:10:23.000000000 +0200
@@ -0,0 +1,74 @@
+#ifndef _LINUX_PAGE_H
+#define _LINUX_PAGE_H
+
+#include <linux/types.h>
+#include <linux/threads.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+
+struct address_space;
+
+/*
+ * Each physical page in the system has a struct page associated with
+ * it to keep track of whatever it is we are using the page for at the
+ * moment. Note that we have no way to track which tasks are using
+ * a page.
+ */
+struct page {
+ unsigned long flags; /* Atomic flags, some possibly
+ * updated asynchronously */
+ atomic_t _count; /* Usage count, see below. */
+ atomic_t _mapcount; /* Count of ptes mapped in mms,
+ * to show when page is mapped
+ * & limit reverse map searches.
+ */
+ union {
+ struct {
+ unsigned long private; /* Mapping-private opaque data:
+ * usually used for buffer_heads
+ * if PagePrivate set; used for
+ * swp_entry_t if PageSwapCache;
+ * indicates order in the buddy
+ * system if PG_buddy is set.
+ */
+ struct address_space *mapping; /* If low bit clear, points to
+ * inode address_space, or NULL.
+ * If page mapped as anonymous
+ * memory, low bit is set, and
+ * it points to anon_vma object:
+ * see PAGE_MAPPING_ANON below.
+ */
+ };
+#if NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS
+ spinlock_t ptl;
+#endif
+ };
+ pgoff_t index; /* Our offset within mapping. */
+ struct list_head lru; /* Pageout list, eg. active_list
+ * protected by zone->lru_lock !
+ */
+ /*
+ * On machines where all RAM is mapped into kernel address space,
+ * we can simply calculate the virtual address. On machines with
+ * highmem some memory is mapped into kernel virtual memory
+ * dynamically, so we need a place to store that address.
+ * Note that this field could be 16 bits on x86 ... ;)
+ *
+ * Architectures with slow multiplication can define
+ * WANT_PAGE_VIRTUAL in asm/page.h
+ */
+#if defined(WANT_PAGE_VIRTUAL)
+ void *virtual; /* Kernel virtual address (NULL if
+ not kmapped, ie. highmem) */
+#endif /* WANT_PAGE_VIRTUAL */
+};
+
+#define page_private(page) ((page)->private)
+#define set_page_private(page, v) ((page)->private = (v))
+
+#ifndef CONFIG_DISCONTIGMEM
+/* The array of struct pages - for discontigmem use pgdat->lmem_map */
+extern struct page *mem_map;
+#endif
+
+#endif /*_LINUX_PAGE_H */