We embed a pointer to the service tree in each queue, to handle multiple
service trees easily.
Service trees are enriched with a counter.
cfq_add_rq_rb is invoked after putting the rq in the fifo, to ensure
that all fields in rq are properly initialized.
Signed-off-by: NCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>