SEEK_HOLE or FIEMAP?

Wonder why good ole' partitions are out of fashion?

Rather than having the ability for applications to do nasty things and 
become dependant on physical block numbers, which prevent copying of files 
around.   You could use a raw partition, and then copy the blocks into 
known offsets from the beginning of the partition.  This seems much 
simpler.

Presumbably a BootFS, with a boot loader friendly structure might also be 
a robust alternative and avoid duplication, of files in the raw partition 
approach.