Hello All,
  
  phys_pud_init is broken when using it at runtime with some offsets.
It currently only maps one pud entry worth of pages while trampling any
mappings that may have existed on the pmd_page :( 

This his patch make it safe to map addresses that are not pmd_page
aligned and generally more robust.  

This is a critical patch for hot-add and x86_64. 

Thanks to Dave Hansen for input on look and feel of this patch and it's
constructs. 

This was built against 2.6.18-rc2.

Signed-off-by:  Keith Mannthey <kmannth@us.ibm.com>