[PATCH] own header file for struct page

This moves the definition of struct page from mm.h to its own header file
page-struct.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 avoid 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>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 67 insertions, 0 deletions

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
new file mode 100644
index 000000000000..c3852fd4a1cc
--- /dev/null
+++ b/include/linux/mm_types.h
@@ -0,0 +1,67 @@
+#ifndef _LINUX_MM_TYPES_H
+#define _LINUX_MM_TYPES_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, though if it is a pagecache page, rmap structures can tell us
+ * who is mapping it.
+ */
+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 */
+};
+
+#endif /* _LINUX_MM_TYPES_H */