For some cases, ops->get_reset_level may not be implemented, so we
should check whether it is NULL before calling get_reset_level.
Signed-off-by: NGuangbin Huang <huangguangbin@huawei.com>
Signed-off-by: NHuazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>