fs/ubifs: use rbtree postorder iteration helper instead of opencoding

Use rbtree_postorder_for_each_entry_safe() to destroy the rbtree instead
of opencoding an alternate postorder iteration that modifies the tree

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ubifs/orphan.c b/fs/ubifs/orphan.c
index ba32da3..f1c3e5a1 100644
--- a/fs/ubifs/orphan.c
+++ b/fs/ubifs/orphan.c
@@ -815,27 +815,10 @@
 
 static void dbg_free_check_tree(struct rb_root *root)
 {
-	struct rb_node *this = root->rb_node;
-	struct check_orphan *o;
+	struct check_orphan *o, *n;
 
-	while (this) {
-		if (this->rb_left) {
-			this = this->rb_left;
-			continue;
-		} else if (this->rb_right) {
-			this = this->rb_right;
-			continue;
-		}
-		o = rb_entry(this, struct check_orphan, rb);
-		this = rb_parent(this);
-		if (this) {
-			if (this->rb_left == &o->rb)
-				this->rb_left = NULL;
-			else
-				this->rb_right = NULL;
-		}
+	rbtree_postorder_for_each_entry_safe(o, n, root, rb)
 		kfree(o);
-	}
 }
 
 static int dbg_orphan_check(struct ubifs_info *c, struct ubifs_zbranch *zbr,