how to get PFN of page cache in guest OS?

i want to develop the linux kernel module that detct PFN of page cache and its corresponding disk block number. so how to get PFN of page cache?. i use this module in VM live migration and use KVM hypervisor. i am trying to reduce total migration time. instead of migrating page cache at remote host, pagecache restore from the disk storage before VM resume at remote host.