[Qemu-block] [PATCH v6 00/14] Add support for io_uring

[Aarushi Mehta]

This patch series adds support for the newly developed io_uring Linux AIO
interface. Linux io_uring is faster than Linux's AIO asynchronous I/O code,
offers efficient buffered asynchronous I/O support, the ability to do I/O
without performing a system call via polled I/O, and other efficiency 
enhancements.

Testing it requires a host kernel (5.1+) and the liburing library.
Use the option -drive aio=io_uring to enable it.

Benchmarks for the system at https://github.com/rooshm/benchmarks
io_uring has similar performance as libaio but supports cache=writeback.
Further performance enhancement will be implemented

There is currently an -EIO output when guests are booted from io_uring
disks for the second time with clean shutdowns that is being investigated.

v6:
- add slow path for short-read
- hooks up fsync
- enables qemu-iotests with aio options
- adds bdrv_parse_aio

v5:
- Adds completion polling
- Extends qemu-io
- Adds qemu-iotest

v4:
- Add error handling
- Add trace events
- Remove aio submission based code

Aarushi Mehta (14):
  configure: permit use of io_uring
  qapi/block-core: add option for io_uring
  block/block: add BDRV flag for io_uring
  block/io_uring: implements interfaces for io_uring
  stubs: add stubs for io_uring interface
  util/async: add aio interfaces for io_uring
  blockdev: accept io_uring as option
  block/file-posix.c: extend to use io_uring
  block: add trace events for io_uring
  block/io_uring: adds userspace completion polling
  qemu-io: adds option to use aio engine
  qemu-img: adds option to use aio engine
  qemu-nbd: adds option for aio engines
  tests/qemu-iotest: enable testing with qemu-io aio options

 MAINTAINERS                  |   8 +
 block.c                      |  22 ++
 block/Makefile.objs          |   3 +
 block/file-posix.c           |  99 ++++++--
 block/io_uring.c             | 439 +++++++++++++++++++++++++++++++++++
 block/trace-events           |  12 +
 blockdev.c                   |  12 +-
 configure                    |  27 +++
 include/block/aio.h          |  16 +-
 include/block/block.h        |   2 +
 include/block/raw-aio.h      |  12 +
 qapi/block-core.json         |   4 +-
 qemu-img.c                   |  11 +-
 qemu-io.c                    |  25 +-
 qemu-nbd.c                   |  12 +-
 stubs/Makefile.objs          |   1 +
 stubs/io_uring.c             |  32 +++
 tests/qemu-iotests/check     |  14 +-
 tests/qemu-iotests/common.rc |  10 +
 util/async.c                 |  36 +++
 20 files changed, 746 insertions(+), 51 deletions(-)
 create mode 100644 block/io_uring.c
 create mode 100644 stubs/io_uring.c

-- 
2.21.0