For the error '202803 – Hibernation does not work with BTRFS and swapfile on 5.0 kernel. Cannot find swap device.'

• btrfs physical_location is different from normal filefrag physical address.
• There is a tool to get the physical address of the swapfile in the comments

The full process is described here: https://wiki.archlinux.org/title/Power_management/Suspend_and_hibernate#Hibernation_into_swap_file_on_Btrfs

Remember to divide by pagesize!