vdev_queue_class_tree
avl_create(vdev_queue_class_tree(vq, p), compfn,
avl_destroy(vdev_queue_class_tree(vq, p));
avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio);
avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio);
if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
tree = vdev_queue_class_tree(vq, p);
tree = vdev_queue_class_tree(vq, zio->io_priority);
avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio);
avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio);