So, this patch started out with me trying to keep from passing
contiguous, node-specific mem_map into free_area_init_node() and
cousins.  Instead, I relied on some calls to pfn_to_page().

This works fine and dandy when all you need is the pgdat->node_mem_map
to do pfn_to_page().  However, the non-NUMA/DISCONTIG architectures use
the real, global mem_map[] instead of a node_mem_map in the
pfn_to_page() calculation.  So, I ended up effectively trying to
initialize mem_map from itself, when it was NULL.  That was bad, and
caused some very pretty colors on someone's screen when he tested it.

So, I had to make sure to initialize the global mem_map[] before calling
into free_area_init_node().  Then, I realized how many architectures do
this on their own, and have comments like this:

	/* XXX: MRB-remove - this doesn't seem sane, should this be done somewhere else ?*/
	mem_map = NODE_DATA(0)->node_mem_map;

Also, ppc64 has some interesting hacks^Wcode in this area to make up for
any empty-memory NUMA nodes, which I think can go away now.

The following patch does what my first one did (don't pass mem_map into
the init functions), incorporates Jesse Barnes' ia64 fixes on top of
that, and gets rid of all but one of the global mem_map initializations
(parisc is weird).  It also magically removes more code than it adds. 
It could be smaller, but I shamelessly added some comments.  

 arch/alpha/mm/numa.c             |    2 -
 arch/arm/mm/init.c               |    6 ----
 arch/arm26/mm/init.c             |    4 ---
 arch/cris/arch-v10/mm/init.c     |    3 --
 arch/i386/mm/discontig.c         |   11 +++-----
 arch/ia64/mm/contig.c            |    7 ++---
 arch/ia64/mm/discontig.c         |    4 +--
 arch/ia64/mm/init.c              |    8 +++---
 arch/mips/sgi-ip27/ip27-memory.c |    2 -
 arch/parisc/mm/init.c            |    2 -
 arch/ppc64/mm/init.c             |    3 --
 arch/ppc64/mm/numa.c             |   12 ---------
 arch/sh/mm/init.c                |    6 +---
 arch/sh64/mm/init.c              |    5 ---
 arch/sparc/mm/srmmu.c            |    3 --
 arch/sparc/mm/sun4c.c            |    3 --
 arch/sparc64/mm/init.c           |    3 --
 arch/v850/kernel/setup.c         |    3 --
 arch/x86_64/mm/numa.c            |    2 -
 include/asm-ia64/pgtable.h       |    2 -
 include/linux/mm.h               |    5 +--
 mm/page_alloc.c                  |   51 +++++++++++++++++++++++++--------------
 22 files changed, 66 insertions(+), 81 deletions(-)

-- Dave