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>

1 files changed, 4 insertions, 5 deletions

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 0a0ab8e21b19..c5bc355d8243 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -397,17 +397,16 @@ static void hugetlbfs_evict_inode(struct inode *inode)
 }
 
 static inline void
-hugetlb_vmtruncate_list(struct prio_tree_root *root, pgoff_t pgoff)
+hugetlb_vmtruncate_list(struct rb_root *root, pgoff_t pgoff)
 {
 	struct vm_area_struct *vma;
-	struct prio_tree_iter iter;
 
-	vma_prio_tree_foreach(vma, &iter, root, pgoff, ULONG_MAX) {
+	vma_interval_tree_foreach(vma, root, pgoff, ULONG_MAX) {
 		unsigned long v_offset;
 
 		/*
 		 * Can the expression below overflow on 32-bit arches?
-		 * No, because the prio_tree returns us only those vmas
+		 * No, because the interval tree returns us only those vmas
 		 * which overlap the truncated area starting at pgoff,
 		 * and no vma on a 32-bit arch can span beyond the 4GB.
 		 */
@@ -432,7 +431,7 @@ static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
 
 	i_size_write(inode, offset);
 	mutex_lock(&mapping->i_mmap_mutex);
-	if (!prio_tree_empty(&mapping->i_mmap))
+	if (!RB_EMPTY_ROOT(&mapping->i_mmap))
 		hugetlb_vmtruncate_list(&mapping->i_mmap, pgoff);
 	mutex_unlock(&mapping->i_mmap_mutex);
 	truncate_hugepages(inode, offset);