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>