ppc64 has constraints on the mixing of small and large pages, such that
they cannot be mixed in the same 256Mb segment.  This patch provides an
architecture specific arch_get_unmapped_area_topdown() which implements
these contraints.
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>