The hugetlb_page test in do_munmap is too permissive.  It checks start vma,
but forgets that end vma might be different and huge though start is not:
so hits unmap_hugepage_range BUG if misaligned end was given.

And it's too restrictive: munmap has always succeeded on unmapped areas
within its range, why should it behave differently near a hugepage vma?

And the additional checks in is_aligned_hugepage_range are irrelevant here,
when the hugepage vma already exists.  But the function is still required
(on some arches), as the default for prepare_hugepage_range - leave
renaming cleanup to another occasion.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: William Irwin <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>