pcpu_off_to_block_off
int block_off = pcpu_off_to_block_off(*bit_off);
int block_off = pcpu_off_to_block_off(*bit_off);
int s_off = pcpu_off_to_block_off(bit_off);
s_off = pcpu_off_to_block_off(bit_off);
e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
s_off = pcpu_off_to_block_off(bit_off);
e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;