[PATCH V8 0/4] blk-mq: implement queue quiesce via percpu_ref for BLK_MQ_F_BLOCKING

[Ming Lei]

Hi Jens,

The 1st patch add .mq_quiesce_mutex for serializing quiesce/unquiesce,
and prepares for replacing srcu with percpu_ref.

The 2nd patch replaces srcu with percpu_ref.

The 3rd patch adds tagset quiesce interface.

The 4th patch applies tagset quiesce interface for NVMe subsystem.

V8:
	- rebase on latest linus tree, only there is small fuzz change on 2/4

V7:
	- base on latest for-5.10/block, only there is small change on 2/4

V6:
	- base on for-5.10/block directly, instead of being against on patchset of
	'percpu_ref & block: reduce memory footprint of percpu_ref in fast path',
	because these patches don't depend on that patchset. 

V5:
	- warn once in case that driver unquiesces its queue being
	  quiesce and not done, only patch 2 is modified

V4:
	- remove .mq_quiesce_mutex, and switch to test_and_[set|clear] for
	avoiding duplicated quiesce action
	- pass blktests(block, nvme)

V3:
	- add tagset quiesce interface
	- apply tagset quiesce interface for NVMe
	- pass blktests(block, nvme)

V2:
	- add .mq_quiesce_lock
	- add comment on patch 2 wrt. handling hctx_lock() failure
	- trivial patch style change


Ming Lei (3):
  block: use test_and_{clear|test}_bit to set/clear QUEUE_FLAG_QUIESCED
  blk-mq: implement queue quiesce via percpu_ref for BLK_MQ_F_BLOCKING
  blk-mq: add tagset quiesce interface

Sagi Grimberg (1):
  nvme: use blk_mq_[un]quiesce_tagset

 block/blk-core.c         |  13 +++
 block/blk-mq-sysfs.c     |   2 -
 block/blk-mq.c           | 182 +++++++++++++++++++++++++--------------
 block/blk-sysfs.c        |   6 +-
 block/blk.h              |   2 +
 drivers/nvme/host/core.c |  19 ++--
 include/linux/blk-mq.h   |  10 +--
 include/linux/blkdev.h   |   4 +
 8 files changed, 154 insertions(+), 84 deletions(-)

Cc: Hannes Reinecke <hare at suse.de>
Cc: Sagi Grimberg <sagi at grimberg.me>
Cc: Bart Van Assche <bvanassche at acm.org>
Cc: Johannes Thumshirn <Johannes.Thumshirn at wdc.com>
Cc: Chao Leng <lengchao at huawei.com>
-- 
2.25.2