[RFC PATCH 0/7] ublk: support to register bvec buffer automatically

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

Hello Jens,

This patch tries to address limitation from in-tree ublk zero copy:

- one IO needs two extra uring_cmd for register/unregister bvec buffer, not
  efficient

- introduced dependency on the two uring_cmd, so the buffer consumer has to
linked with the two uring_cmd, hard to use & less efficient

This patchset adds feature UBLK_F_AUTO_BUF_REG:

- register request buffer automatically before delivering io command to ublk server

- unregister request buffer automatically when completing the request

- both io_uring context and buffer index can be specified from ublk
  uring_cmd header

With this way, 'fio/t/io_uring -p0 /dev/ublkb0' shows that IOPS is improved
by 50% compared with F_SUPPORT_ZERO_COPY in my test VM.

kernel selftests are added for covering both function & stress test.

Please review & comment!

Thanks,
Ming

Ming Lei (7):
  io_uring: add 'struct io_buf_data' for register/unregister bvec buffer
  io_uring: add helper __io_buffer_[un]register_bvec
  io_uring: support to register bvec buffer to specified io_uring
  ublk: convert to refcount_t
  ublk: prepare for supporting to register request buffer automatically
  ublk: register buffer to specified io_uring & buf index via
    UBLK_F_AUTO_BUF_REG
  selftests: ublk: support UBLK_F_AUTO_BUF_REG

 drivers/block/ublk_drv.c                      | 165 ++++++++++++++----
 include/linux/io_uring/cmd.h                  |  15 +-
 include/uapi/linux/ublk_cmd.h                 |  38 ++++
 io_uring/rsrc.c                               | 141 ++++++++++-----
 tools/testing/selftests/ublk/Makefile         |   2 +
 tools/testing/selftests/ublk/file_backed.c    |  12 +-
 tools/testing/selftests/ublk/kublk.c          |  24 ++-
 tools/testing/selftests/ublk/kublk.h          |   6 +
 tools/testing/selftests/ublk/null.c           |  43 +++--
 tools/testing/selftests/ublk/stripe.c         |  21 +--
 .../testing/selftests/ublk/test_generic_08.sh |  32 ++++
 .../testing/selftests/ublk/test_stress_03.sh  |   6 +
 .../testing/selftests/ublk/test_stress_04.sh  |   6 +
 .../testing/selftests/ublk/test_stress_05.sh  |   8 +
 14 files changed, 409 insertions(+), 110 deletions(-)
 create mode 100755 tools/testing/selftests/ublk/test_generic_08.sh

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2.47.0