[PATCH V5 00/25] block: unify elevator changing and fix lockdep warning

[Ming Lei <ming.lei@redhat.com>]

Hello Jens,

This patchset cleans up elevator change code, and unifying it via single
helper, meantime moves kobject_add/del & debugfs register/unregister out of
queue freezing & elevator_lock. This way fixes many lockdep warnings
reported recently, especially since fs_reclaim is connected with freeze lock
manually by commit ffa1e7ada456 ("block: Make request_queue lockdep splats
show up earlier").


Thanks,
Ming

V5:
	- replace down_read_nested() with down_read(), by adding
	  helper of add_disk_final()

	- fix race between elv_iosched_store and __del_gendisk (Nilay Shoff)

	- improve elv_update_nr_hw_queues() (Christoph)

V4:
	- pull Christoph's two elevator change/switch cleanup patches first,
	then the following elevator change unifying is simplified a lot(Christoph)

	- fold Nilay's patch into the last patch for avoiding one new
	lock warning on rqos_state_mutex (Nilay Shoff)

	- drop patch "block: move blk_unregister_queue() & device_del() after freeze
	wait" which may cause MD hang during shutdown, and add new patch "block: add
    new helper for disabling elevator switch when deleting disk" for dealing with
    one small race window (Christoph)

	- add patch "block: remove elevator queue's type check in elv_attr_show/store()"
	(Christoph)

    - rename ->update_nr_hwq_sema as ->update_nr_hwq_lock (Christoph)

	- add small patch "block: move blk_queue_registered() check into elv_iosched_store()"

V3:
	- replace srcu with rw_sem for avoiding race between add/del disk &
	  elevator switch and updating nr_hw_queues (Nilay Shoff)

	- add elv_update_nr_hw_queues() for elevator reattachment in case of
	updating nr_hw_queues, meantime keep elv_change_ctx as local structure
	(Christoph)

	- replace ->elevator_lock with disk->rqos_state_mutex for covering wbt
	state change

	- add new patch "block: use q->elevator with ->elevator_lock held in elv_iosched_show()"

	- small cleanup & commit log improvement

V2:
	- retry add/del disk when blk_mq_update_nr_hw_queues() is in-progress

	- swap blk_mq_add_queue_tag_set() with blk_mq_map_swqueue() in
	blk_mq_init_allocated_queue() (Nilay Shroff)

	- move ELEVATOR_FLAG_DISABLE_WBT to request queue's flags (Nilay Shoff) 

	- fix race because of delaying elevator unregister

	- define flags of `elv_change_ctx` as `bool` (Christoph)

	- improve comment and commit log (Christoph)



Christoph Hellwig (2):
  block: look up the elevator type in elevator_switch
  block: fold elevator_disable into elevator_switch

Ming Lei (23):
  block: move blk_mq_add_queue_tag_set() after blk_mq_map_swqueue()
  block: move ELEVATOR_FLAG_DISABLE_WBT a request queue flag
  block: don't call freeze queue in elevator_switch() and
    elevator_disable()
  block: use q->elevator with ->elevator_lock held in elv_iosched_show()
  block: add two helpers for registering/un-registering sched debugfs
  block: move sched debugfs register into elvevator_register_queue
  block: add helper add_disk_final()
  block: prevent adding/deleting disk during updating nr_hw_queues
  block: don't allow to switch elevator if updating nr_hw_queues is
    in-progress
  block: move blk_queue_registered() check into elv_iosched_store()
  block: simplify elevator reattachment for updating nr_hw_queues
  block: move queue freezing & elevator_lock into elevator_change()
  block: add `struct elv_change_ctx` for unifying elevator change
  block: unifying elevator change
  block: pass elevator_queue to elv_register_queue & unregister_queue
  block: remove elevator queue's type check in elv_attr_show/store()
  block: fail to show/store elevator sysfs attribute if elevator is
    dying
  block: add new helper for disabling elevator switch when deleting disk
  block: move elv_register[unregister]_queue out of elevator_lock
  block: move hctx debugfs/sysfs registering out of freezing queue
  block: don't acquire ->elevator_lock in blk_mq_map_swqueue and
    blk_mq_realloc_hw_ctxs
  block: move hctx cpuhp add/del out of queue freezing
  block: move wbt_enable_default() out of queue freezing from sched
    ->exit()

 block/bfq-iosched.c    |   6 +-
 block/blk-mq-debugfs.c |  13 +-
 block/blk-mq-sched.c   |  41 +++--
 block/blk-mq.c         | 132 +++--------------
 block/blk-sysfs.c      |  29 ++--
 block/blk-wbt.c        |   9 +-
 block/blk.h            |   8 +-
 block/elevator.c       | 329 ++++++++++++++++++++++++-----------------
 block/elevator.h       |   6 +-
 block/genhd.c          | 197 +++++++++++++++---------
 include/linux/blk-mq.h |   3 +
 include/linux/blkdev.h |   8 +
 12 files changed, 402 insertions(+), 379 deletions(-)

-- 
2.47.0