r46: - Convert convergent_req->completed to atomic_t
r46: - Convert convergent_req->completed to atomic_t

- Allow read/write of chunk to be split among more than one bio (in case
we hit queue limits for large chunks).  Track I/O errors from completing
bios and report them at the end.  Don't keep pointers to chunk bios in
flight, since the primary object is the scatterlist anyway.

- Rename chunk scatterlist again

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr