bio is used in bfq-mq's get_rq_priv, to get the request group. We could
pass directly the group here, but I thought that passing the bio was
more general, giving the possibility to get other pieces of information
if needed.
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@fb.com>