[PATCH] no buddy bitmap patch revist: intro and includes

Followings are patches for removing bitmaps from the buddy allocator.  This
is benefical to memory-hot-plug stuffs, because this removes a data
structure which must meet to a host's physical memory layout.

This is one step to manage physical memory in nonlinear / discontiguous way
and will reduce some amounts of codes to implement memory-hot-plug.

This patch removes bitmaps from zone->free_area[] in include/linux/mmzone.h,
and adds some comments on page->private field in include/linux/mm.h.

non-atomic ops for changing PG_private bit is added in include/page-flags.h.
zone->lock is always acquired when PG_private of "a free page" is changed.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/mm.h

@@ -232,6 +232,8 @@ struct page {
 					 * usually used for buffer_heads
 					 * if PagePrivate set; used for
 					 * swp_entry_t if PageSwapCache
+					 * When page is free, this indicates
+					 * order in the buddy system.
 					 */
 	struct address_space *mapping;	/* If low bit clear, points to
 					 * inode address_space, or NULL.

include/linux/mmzone.h

@@ -22,7 +22,6 @@
 
 struct free_area {
 	struct list_head	free_list;
-	unsigned long		*map;
 	unsigned long		nr_free;
 };
 

include/linux/page-flags.h

@@ -239,6 +239,8 @@ extern unsigned long __read_page_state(unsigned offset);
 #define SetPagePrivate(page)	set_bit(PG_private, &(page)->flags)
 #define ClearPagePrivate(page)	clear_bit(PG_private, &(page)->flags)
 #define PagePrivate(page)	test_bit(PG_private, &(page)->flags)
+#define __SetPagePrivate(page)  __set_bit(PG_private, &(page)->flags)
+#define __ClearPagePrivate(page) __clear_bit(PG_private, &(page)->flags)
 
 #define PageWriteback(page)	test_bit(PG_writeback, &(page)->flags)
 #define SetPageWriteback(page)						\