hugepage: Fix hugepage logic in free_pgtables() harder

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Sigh.  Turns out the hugepage logic in free_pgtables() was doubly
broken.  The loop coalescing multiple normal page VMAs into one call
to free_pgd_range() had an off by one error, which could mean it would
coalesce one hugepage VMA into the same bundle (checking 'vma' not
'next' in the loop).  I transferred this bug into the new
is_vm_hugetlb_page() based version.  Here's the fix.

This one didn't bite on powerpc previously for the same reason the
is_hugepage_only_range() problem didn't: powerpc's
hugetlb_free_pgd_range() is identical to free_pgd_range().  It didn't
bite on ia64 because the hugepage region is distant enough from any
other region that the separated PMD_SIZE distance test would always
prevent coalescing the two together.

No libhugetlbfs testsuite regressions (ppc64, POWER5).

Signed-off-by: David Gibson <[email protected]>

Index: working-2.6/mm/memory.c
--- working-2.6.orig/mm/memory.c	2006-03-03 11:39:33.000000000 +1100
+++ working-2.6/mm/memory.c	2006-03-03 11:39:50.000000000 +1100
@@ -285,7 +285,7 @@ void free_pgtables(struct mmu_gather **t
 			 * Optimization: gather nearby vmas into one call down
 			while (next && next->vm_start <= vma->vm_end + PMD_SIZE
-			       && !is_vm_hugetlb_page(vma)) {
+			       && !is_vm_hugetlb_page(next)) {
 				vma = next;
 				next = vma->vm_next;

David Gibson			| I'll have my music baroque, and my code
david AT	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
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