Signed-off-by: Wangweizhen <hawking.rei@gmail.com>

UCP https://github.com/tikv/tikv/issues/6496

Fix this error from clippy.

```
this public function dereferences a raw pointer but is not marked `unsafe`
help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#not_unsafe_ptr_arg_deref

```