How to mmap a file in linux kernel space?

Question

I try to mmap a file in a linux kernel module. I have tried to use the function do_mmap_pgoff. But the address returned is memory virtual address in current process' user space, i.e., below the kernel boundary. Instead, I want to map the file in the kernel space and get the kernel virtual address of the mapped region. Is there any kernel API in Linux support this operation? Thanks