Copy contents of data buffers from one chain of bios to another
void bio_copy_data(struct bio * dst, struct bio * src);
dst
destination bio list
src
source bio list
If src and dst are single bios, bi_next must be NULL - otherwise, treats src and dst as linked lists of bios.
Stops when it reaches the end of either src or dst - that is, copies min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of bios).