[PATCH] drm/mm: Fix caching of leftmost node in the interval tree

[Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>]

When we descend the tree to find our slot, if we step to the right, we
are no longer the leftmost node.

Fixes: f808c13fd373 ("lib/interval_tree: fast overlap detection")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
---
 drivers/gpu/drm/drm_mm.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 186c4e90cc1c..a351bd888a61 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -180,7 +180,7 @@ static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
 	struct drm_mm *mm = hole_node->mm;
 	struct rb_node **link, *rb;
 	struct drm_mm_node *parent;
-	bool leftmost = true;
+	bool leftmost;
 
 	node->__subtree_last = LAST(node);
 
@@ -201,6 +201,7 @@ static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
 	} else {
 		rb = NULL;
 		link = &mm->interval_tree.rb_root.rb_node;
+		leftmost = true;
 	}
 
 	while (*link) {
@@ -208,11 +209,11 @@ static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
 		parent = rb_entry(rb, struct drm_mm_node, rb);
 		if (parent->__subtree_last < node->__subtree_last)
 			parent->__subtree_last = node->__subtree_last;
-		if (node->start < parent->start)
+		if (node->start < parent->start) {
 			link = &parent->rb.rb_left;
-		else {
+		} else {
 			link = &parent->rb.rb_right;
-			leftmost = true;
+			leftmost = false;
 		}
 	}
 
-- 
2.16.1