On Mon, Feb 05, 2024 at 02:37:41PM +0900, Damien Le Moal wrote: > OK. So I think that Hannes'idea to get/put the queue usage counter reference > based on a zone BIO plug becoming not empty (get ref) and becoming empty (put > ref) may be simpler then. And that would also work in the same way for blk-mq > and BIO based drivers. Maybe I'm missing something, but I'm not sure how that would even work. We need a q_usage_counter ref when doing all the submissions checks (limits, bounce, etc) early in blk_mq_sunmit_bio, and that one should be taken using the mormal bio_queue_enter patch to do the right thing on nowait submissions, when the queue is already frozen, etc. What is the benefit of not just keeping that references vs releasing it for all but the first bio just so that we need to grab another new reference at the actual submission time?
