nvmet: cancel fatal error and flush async work before free controller

Make sure they are not running and we can free the controller
safely.
Signed-off-by: NRoy Shterman <roys@lightbitslabs.com>
Signed-off-by: NSagi Grimberg <sagi@grimberg.me>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

drivers/nvme/target/core.c

@@ -816,6 +816,9 @@ static void nvmet_ctrl_free(struct kref *ref)
 	list_del(&ctrl->subsys_entry);
 	mutex_unlock(&subsys->lock);
 
+	flush_work(&ctrl->async_event_work);
+	cancel_work_sync(&ctrl->fatal_err_work);
+
 	ida_simple_remove(&subsys->cntlid_ida, ctrl->cntlid);
 	nvmet_subsys_put(subsys);