From: Christophe Saout <christophe@saout.de>

The intent of these are to clarify the meaning of the bio fields in the
bi_end_io function (since we are already mostly there).  After these small
modifications bio->bi_idx and the corresponding bio_iovec(bio)->bv_offset
point to the beginning of the completed data, together with the nr_bytes
argument you know exactly what data was finished, e.g.  when you can't
track it otherwise (or it would be unnecessary expensive).  Apart from that
it's a nice-to-have.

The first mini-patch moves the update of bio_iovec(bio)->bv_offset and
->bv_len after the call of bi_end_io where bi_idx gets updated so they get
updated together.  Ok with Jens.

The second part of the patch modifies the multwrite hack in PIO non-
taskfile ide disk code.  It modifies the bi_idx field to walk the bios and
doesn't reset it correctly before ending the request.  The patch uses the
segment counter in the request field to correctly restore the bi_idx field
before ending the request.  Can't possibly break anything since it's
working on the local request copy ("scratchpad") anyway.  Also does this in
legacy/pdc4030.c (similar code).  The code modified here is going to die
anyway any trying to fix it would be too invasive.  Ok with Bartlomiej.