When using CONFIG_NONLINEAR, a zone's mem_map isn't contiguous, and
isn't allocated in the same place.  This means that nonlinear doesn't
really have a mem_map[] to pass into free_area_init_node() or 
memmap_init_zone() which makes any sense.  

So, this patch removes the 'struct page *mem_map' argument to both of
those functions.  All non-NUMA architectures just pass a NULL in there,
which is ignored.  The solution on the NUMA arches is to pass the
mem_map in via the pgdat, which works just fine. 

To replace the removed arguments, a call to pfn_to_page(node_start_pfn)
is made.  This is valid because all of the pfn_to_page() implementations
rely only on the pgdats, which are already set up at this time.  Plus,
the pfn_to_page() method should work for any future nonlinear-type
code.  

Finally, the patch creates a function: node_alloc_mem_map(), which I
plan to effectively #ifdef out for nonlinear at some future date.  

Compile tested and booted on SMP x86, NUMAQ, and ppc64.  Jesse Barnes
said he gave it a run on an ia64 box, and needed one additional patch:

http://marc.theaimsgroup.com/?l=linux-kernel&m=109105562606682&q=raw

Jesse, could you follow up to this mail with a copy of your patch?

Attached patch is against 2.6.8-rc2-mm2.

-- Dave