[Qemu-block] [PATCH v2 00/13] block: bdrv_set_aio_context() related fixes

[Kevin Wolf]

Background for this series is the following bug report, which is about a
crash with virtio-blk + iothread and request resubmission for werror/rerror:

https://bugzilla.redhat.com/show_bug.cgi?id=1671173

The reason is that bdrv_set_aio_context() didn't correctly quiesce
everything. Instead, it had a local hack to call aio_poll() for the
source AioContext, which covered some, but not all cases, and is wrong
because you can only call aio_poll() from the home thread.

So this series tries to make bdrv_drain() actually drain the known cases
(fixes virtio-blk and the NBD client) and use the regular drain
functions in bdrv_set_aio_context() instead of open-coding something
similar.

v2:
- New patch 5: Remove now redundant assignments [Paolo]
- Patch 8 (was 7): Instead of using aio_co_schedule() to switch the
  AioContext and modifying the coroutine code, enter the coroutine in a
  BH in the new AioContext and bdrv_dec_in_flight() in that BH [Paolo]
- Patch 12 (was 11): Cover new == old case in comment [Eric]

Kevin Wolf (13):
  block-backend: Make blk_inc/dec_in_flight public
  virtio-blk: Increase in_flight for request restart BH
  nbd: Restrict connection_co reentrance
  io: Make qio_channel_yield() interruptible
  io: Remove redundant read/write_coroutine assignments
  nbd: Move nbd_read_eof() to nbd/client.c
  nbd: Use low-level QIOChannel API in nbd_read_eof()
  nbd: Increase bs->in_flight during AioContext switch
  block: Don't poll in bdrv_set_aio_context()
  block: Fix AioContext switch for drained node
  test-bdrv-drain: AioContext switch in drained section
  block: Use normal drain for bdrv_set_aio_context()
  aio-posix: Assert that aio_poll() is always called in home thread

 block/nbd-client.h             |  1 +
 include/block/nbd.h            |  3 +-
 include/io/channel.h           |  9 ++++--
 include/sysemu/block-backend.h |  2 ++
 nbd/nbd-internal.h             | 19 -------------
 block.c                        | 26 ++++++++---------
 block/block-backend.c          |  4 +--
 block/nbd-client.c             | 36 +++++++++++++++++++++--
 hw/block/virtio-blk.c          |  4 +++
 io/channel.c                   | 24 ++++++++++------
 nbd/client.c                   | 52 ++++++++++++++++++++++++++++++++--
 tests/test-bdrv-drain.c        | 32 +++++++++++++++++++++
 util/aio-posix.c               |  3 +-
 13 files changed, 164 insertions(+), 51 deletions(-)

-- 
2.20.1