These functions are exported, add pointer checking at the beginning
can make them more safe.
Signed-off-by: NYonglong Liu <liuyonglong@huawei.com>
Signed-off-by: NPeng Li <lipeng321@huawei.com>
Signed-off-by: NHuazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>