[V5,00/12] block: support bio based io polling

Message

Ming Lei April 1, 2021, 2:19 a.m. UTC

Hi Jens,

Add per-task io poll context for holding HIPRI blk-mq/underlying bios
queued from bio based driver's io submission context, and reuse one bio
padding field for storing 'cookie' returned from submit_bio() for these
bios. Also explicitly end these bios in poll context by adding two
new bio flags.

In this way, we needn't to poll all underlying hw queues any more,
which is implemented in Jeffle's patches. And we can just poll hw queues
in which there is HIPRI IO queued.

Usually io submission and io poll share same context, so the added io
poll context data is just like one stack variable, and the cost for
saving bios is cheap.

V5:
	- fix one use-after-free issue in case that polling is from another
	context: adds one new cookie of BLK_QC_T_NOT_READY for preventing
	this issue in patch 8/12
	- add reviewed-by & tested-by tag

V4:
	- cover one more test_bit(QUEUE_FLAG_POLL, ...) suggested by
	  Jeffle(01/12)
	- drop patch of 'block: add helper of blk_create_io_context'
	- add new helper of blk_create_io_poll_context() (03/12)
	- drain submission queues in exit_io_context(), suggested by
	  Jeffle(08/13)
	- considering shared io context case for blk_bio_poll_io_drain()
	(08/13)
	- fix one issue in blk_bio_poll_pack_groups() as suggested by
	Jeffle(08/13)
	- add reviewed-by tag
V3:
	- fix cookie returned for bio based driver, as suggested by Jeffle Xu
	- draining pending bios when submission context is exiting
	- patch style and comment fix, as suggested by Mike
	- allow poll context data to be NULL by always polling on submission queue
	- remove RFC, and reviewed-by

V2:
	- address queue depth scalability issue reported by Jeffle via bio
	group list. Reuse .bi_end_io for linking bios which share same
	.bi_end_io, and support 32 such groups in submit queue. With this way,
	the scalability issue caused by kfifio is solved. Before really
	ending bio, .bi_end_io is recovered from the group head.



Jeffle Xu (4):
  block/mq: extract one helper function polling hw queue
  block: add queue_to_disk() to get gendisk from request_queue
  block: add poll_capable method to support bio-based IO polling
  dm: support IO polling for bio-based dm device

Ming Lei (8):
  block: add helper of blk_queue_poll
  block: add one helper to free io_context
  block: create io poll context for submission and poll task
  block: add req flag of REQ_POLL_CTX
  block: add new field into 'struct bvec_iter'
  block: prepare for supporting bio_list via other link
  block: use per-task poll context to implement bio based io polling
  blk-mq: limit hw queues to be polled in each blk_poll()

 block/bio.c                   |   5 +
 block/blk-core.c              | 258 ++++++++++++++++++++++++++--
 block/blk-ioc.c               |  15 +-
 block/blk-mq.c                | 308 +++++++++++++++++++++++++++++++++-
 block/blk-sysfs.c             |  16 +-
 block/blk.h                   |  58 +++++++
 drivers/md/dm-table.c         |  24 +++
 drivers/md/dm.c               |  14 ++
 drivers/nvme/host/core.c      |   2 +-
 include/linux/bio.h           | 132 ++++++++-------
 include/linux/blk_types.h     |  30 +++-
 include/linux/blkdev.h        |   4 +
 include/linux/bvec.h          |   8 +
 include/linux/device-mapper.h |   1 +
 include/linux/iocontext.h     |   2 +
 include/trace/events/kyber.h  |   6 +-
 16 files changed, 788 insertions(+), 95 deletions(-)

Comments

Ming Lei April 9, 2021, 3:39 p.m. UTC | #1

On Thu, Apr 01, 2021 at 10:19:15AM +0800, Ming Lei wrote:
> Hi Jens,
> 
> Add per-task io poll context for holding HIPRI blk-mq/underlying bios
> queued from bio based driver's io submission context, and reuse one bio
> padding field for storing 'cookie' returned from submit_bio() for these
> bios. Also explicitly end these bios in poll context by adding two
> new bio flags.
> 
> In this way, we needn't to poll all underlying hw queues any more,
> which is implemented in Jeffle's patches. And we can just poll hw queues
> in which there is HIPRI IO queued.
> 
> Usually io submission and io poll share same context, so the added io
> poll context data is just like one stack variable, and the cost for
> saving bios is cheap.
> 
> V5:
> 	- fix one use-after-free issue in case that polling is from another
> 	context: adds one new cookie of BLK_QC_T_NOT_READY for preventing
> 	this issue in patch 8/12
> 	- add reviewed-by & tested-by tag

Hello Guys,

Ping...


Thanks,
Ming

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Christoph Hellwig April 12, 2021, 9:46 a.m. UTC | #2

Hi Ming,

I really struggly to review this series.  A lot of the code and
especially code organization is really strange.  For example a
signiciant chunk of the bio based poll logic is added to blk-mq.c where
it obviously does not fit in, and a lot of the patches seems to both
change blk-mq logic and add new bio based logic.  Also the bio poll
logic is split over various patches in a way that is absolutel not
obvious to me.

Can you try to restructure this a bit:

 - move everything that cleans up or improves existing logic to the
   beginning of the series and into separate patches (where that isn't
   already the case)
 - keep the actual bio polling logic together where the functionality
   isn't otherwise useful
 - maybe add a new block/bio-poll.c file to keep all the code togeher?

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