[PATCH] rbtree: fixed reversed RB_EMPTY_NODE and rb_next/prev

The conditions got reserved. Also make rb_next() and rb_prev() check
for the empty condition.

Signed-off-by: Jens Axboe <axboe@suse.de>

block/as-iosched.c

diff --git a/block/as-iosched.c b/block/as-iosched.c
index 6db4943..9d0f15a 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -336,7 +336,7 @@
 
 static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
 {
-	if (!RB_EMPTY_NODE(&arq->rb_node)) {
+	if (RB_EMPTY_NODE(&arq->rb_node)) {
 		WARN_ON(1);
 		return;
 	}
@@ -1039,7 +1039,7 @@
 	struct request *rq = arq->request;
 	const int data_dir = arq->is_sync;
 
-	BUG_ON(!RB_EMPTY_NODE(&arq->rb_node));
+	BUG_ON(RB_EMPTY_NODE(&arq->rb_node));
 
 	as_antic_stop(ad);
 	ad->antic_status = ANTIC_OFF;

include/linux/rbtree.h

diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h
index 8d5382e..344bc34 100644
--- a/include/linux/rbtree.h
+++ b/include/linux/rbtree.h
@@ -133,7 +133,7 @@
 #define	rb_entry(ptr, type, member) container_of(ptr, type, member)
 
 #define RB_EMPTY_ROOT(root)	((root)->rb_node == NULL)
-#define RB_EMPTY_NODE(node)	(rb_parent(node) != node)
+#define RB_EMPTY_NODE(node)	(rb_parent(node) == node)
 #define RB_CLEAR_NODE(node)	(rb_set_parent(node, node))
 
 extern void rb_insert_color(struct rb_node *, struct rb_root *);

lib/rbtree.c

diff --git a/lib/rbtree.c b/lib/rbtree.c
index 1e55ba1..48499c2 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -322,6 +322,9 @@
 {
 	struct rb_node *parent;
 
+	if (rb_parent(node) == node)
+		return NULL;
+
 	/* If we have a right-hand child, go down and then left as far
 	   as we can. */
 	if (node->rb_right) {
@@ -348,6 +351,9 @@
 {
 	struct rb_node *parent;
 
+	if (rb_parent(node) == node)
+		return NULL;
+
 	/* If we have a left-hand child, go down and then right as far
 	   as we can. */
 	if (node->rb_left) {