qThe queue which this applies to.
activeA flag indication if you want sector throttling on
The sector throttling code allows us to put a limit on the number of
sectors pending io to the disk at a given time, sending active nonzero
indicates you will call blk_started_sectors and blk_finished_sectors in
addition to calling blk_started_io and blk_finished_io in order to
keep track of the number of sectors in flight.