[PATCH 0/6] blk-mq: optimize the queue_rqs() support

[chengming . zhou]

From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>

The current queue_rqs() support has limitation that it can't work on
shared tags queue, which is resolved by patch 1-3. We move the account
of active requests to where we really allocate the driver tag.

This is clearer and matched with the unaccount side which now happen
when we put the driver tag. And we can remove RQF_MQ_INFLIGHT, which
was used to avoid double account problem of flush request.

Another problem is that the driver that support queue_rqs() has to
set inflight request table by itself, which is resolved in patch 4.

The patch 5 fixes a potential race problem which may cause false
timeout because of the reorder of rq->state and rq->deadline.

The patch 6 add support queue_rqs() for null_blk, which showed a
3.6% IOPS improvement in fio/t/io_uring benchmark on my test VM.
And we also use it for testing queue_rqs() on shared tags queue.

Thanks for review!

Chengming Zhou (6):
  blk-mq: account active requests when get driver tag
  blk-mq: remove RQF_MQ_INFLIGHT
  blk-mq: support batched queue_rqs() on shared tags queue
  blk-mq: update driver tags request table when start request
  blk-mq: fix potential reorder of request state and deadline
  block/null_blk: add queue_rqs() support

 block/blk-flush.c             | 11 ++-----
 block/blk-mq-debugfs.c        |  1 -
 block/blk-mq.c                | 53 ++++++++++++++------------------
 block/blk-mq.h                | 57 ++++++++++++++++++++++++-----------
 drivers/block/null_blk/main.c | 20 ++++++++++++
 drivers/block/virtio_blk.c    |  2 --
 drivers/nvme/host/pci.c       |  1 -
 include/linux/blk-mq.h        |  2 --
 8 files changed, 84 insertions(+), 63 deletions(-)

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2.41.0