mm: replace vma prio_tree with an interval tree

Implement an interval tree as a replacement for the VMA prio_tree.  The
algorithms are similar to lib/interval_tree.c; however that code can't be
directly reused as the interval endpoints are not explicitly stored in the
VMA.  So instead, the common algorithm is moved into a template and the
details (node type, how to get interval endpoints from the node, etc) are
filled in using the C preprocessor.

Once the interval tree functions are available, using them as a
replacement to the VMA prio tree is a relatively simple, mechanical job.

Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index f1bb534..c9b40e3 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2474,7 +2474,6 @@
 	struct hstate *h = hstate_vma(vma);
 	struct vm_area_struct *iter_vma;
 	struct address_space *mapping;
-	struct prio_tree_iter iter;
 	pgoff_t pgoff;
 
 	/*
@@ -2491,7 +2490,7 @@
 	 * __unmap_hugepage_range() is called as the lock is already held
 	 */
 	mutex_lock(&mapping->i_mmap_mutex);
-	vma_prio_tree_foreach(iter_vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
+	vma_interval_tree_foreach(iter_vma, &mapping->i_mmap, pgoff, pgoff) {
 		/* Do not unmap the current VMA */
 		if (iter_vma == vma)
 			continue;