phys_to_block_id
const unsigned long start_block_id = phys_to_block_id(start);
const unsigned long end_block_id = phys_to_block_id(start + size - 1);
const unsigned long start_block_id = phys_to_block_id(r->base);
const unsigned long end_block_id = phys_to_block_id(r->base + r->size - 1);