Why parted error

[yzn严哲南]

I have a big usb3.0 storage disk
I input a command: mklabel gpt
But return an error message:
Error Partition(s) 16  have been written, but we have been unable to
inform the kernel of the change, probably because it/they are in use.  As a
result, the old partition(s) will remain in use.  You should reboot now before
making further changes.
How to solve the problem?
I am eager to get the answer.
I am very grateful if you solve it.