nvme: add error handling support for add_disk()

We never checked for errors on add_disk() as this function
returned void. Now that this is fixed, use the shiny new
error handling.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -3798,7 +3798,9 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 
 	nvme_get_ctrl(ctrl);
 
-	device_add_disk(ctrl->device, ns->disk, nvme_ns_id_attr_groups);
+	if (device_add_disk(ctrl->device, ns->disk, nvme_ns_id_attr_groups))
+		goto out_cleanup_ns_from_list;
+
 	if (!nvme_ns_head_multipath(ns->head))
 		nvme_add_ns_cdev(ns);
 
@@ -3808,6 +3810,11 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 
 	return;
 
+ out_cleanup_ns_from_list:
+	nvme_put_ctrl(ctrl);
+	down_write(&ctrl->namespaces_rwsem);
+	list_del_init(&ns->list);
+	up_write(&ctrl->namespaces_rwsem);
  out_unlink_ns:
 	mutex_lock(&ctrl->subsys->lock);
 	list_del_rcu(&ns->siblings);