nvme_user_cmd
return nvme_user_cmd(ctrl, NULL, argp, 0, open_for_write);
return nvme_user_cmd(ns->ctrl, ns, argp, flags, open_for_write);
ret = nvme_user_cmd(ctrl, ns, argp, 0, open_for_write);
return nvme_user_cmd(ctrl, NULL, argp, 0, open_for_write);