Hi Jens Two fixes for updating nr_hw_queues. The first patch fixes the following scenario: io scheduler (kyber) depends on the mapping between ctx and hctx. When update nr_hw_queues, io scheduler's init_hctx will be invoked before the mapping is adapted correctly, this would cause panic in kyber. The second patch fixes the following scenario: part_in_flight/rw will invoke blk_mq_in_flight/rw to account the inflight requests. It will access the queue_hw_ctx and nr_hw_queues w/o any protection. When updating nr_hw_queues and blk_mq_in_flight /rw occur concurrently, panic comes up. V4: - remove the elv_type in request_queue and introduce blk_mq_qe_pair to cache the elevator_type associated with one request_queue. And add two new helper interfaces blk_mq_elv_switch_none/back to carry out the elevator_type caching and switching work. - Add Ming's Reviewd-by on 2nd patch and remove it from 1st patch due to the reworking. - comment modification. V3: - move the rcu and q_usage_counter checking into blk_mq_queue_tag_busy_iter as suggestion of Ming. - Add more comment about the __module_get in 1st patch. - Add Ming's Reviewd-by on 1st patch. V2: - remove blk_mq_sched_init/exit_hctx in patch 1. - use q_usage_counter instead of adding new member suggested by Ming in patch 2. - comment modification. block/blk-mq-sched.c | 44 -------------------------------------------- block/blk-mq-sched.h | 5 ----- block/blk-mq-tag.c | 14 +++++++++++++- block/blk-mq.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------- block/blk.h | 2 ++ block/elevator.c | 20 ++++++++++++-------- 6 files changed, 115 insertions(+), 66 deletions(-) Thanks Jianchao
