On Thu, Oct 11, 2018 at 10:59:11AM +0100, John Garry wrote: > > > blk-mq tags are always per-host (which has actually caused problems for > > ATA, which is now using its own per-device tags). > > > > So, for example, if Scsi_host.can_queue = 2048 and Scsi_host.nr_hw_queues = > 16, then rq tags are still in range [0, 2048) for that HBA, i.e. invariant > on queue count? Yes, if can_queue is 2048 you will gets tags from 0..2047. IFF you device needs different tags for different queues it can use the blk_mq_unique_tag heper to generate unique global tag. But unless you actuall have multiple hardware queues that latter part is rather irrelevant to start with.
