[RFC] hugetlb reservations -- MAP_PRIVATE fixes for split vmas

[Andy Whitcroft]

As reported by Adam Litke and Jon Tollefson one of the libhugetlbfs
regression tests triggers a negative overall reservation count.  When
this occurs where there is no dynamic pool enabled tests will fail.

Following this email are two patches to fix this issue:

hugetlb reservations: move region tracking earlier -- simply moves the
  region tracking code earlier so we do not have to supply prototypes, and

hugetlb reservations: fix hugetlb MAP_PRIVATE reservations across vma
  splits -- which moves us to tracking the consumed reservation so that
  we can correctly calculate the remaining reservations at vma close time.

This stack is against the top of v2.6.25-rc6-mm3, should this solution
prove acceptable it would probabally need porting below Nicks multiple
hugepage size patches and those updated; if so I would be happy to do
that too.

Jon could you have a test on this and see if it works out for you.

-apw
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