[PATCH v3 00/10] Refactor bdrv_try_set_aio_context using transactions

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

The aim of this series is to reorganize bdrv_try_set_aio_context
and drop BDS ->set_aio_context and ->can_set_aio_ctx callbacks in
favour of a new one, ->change_aio_ctx.

More informations in patch 3 (which is also RFC, due to the doubts
I have with AioContext locks).

Patch 1 just add assertions in the code, 2 extends the transactions API to be able to add also transactions in the tail
of the list.
Patch 3 is the core of this series, and introduces the new callback.
It is marked as RFC and the reason is explained in the commit message.
Patches 4-5-6 implement ->change_aio_ctx in the various block, blockjob
and block-backend BDSes.
Patch 7 substitutes ->change_aio_ctx with the old callbacks, and
patch 8 takes care of deleting the old callbacks and unused code.

This series is based on "job: replace AioContext lock with job_mutex",
but just because it uses job_set_aio_context() introduced there.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Based-on: <20220706201533.289775-1-eesposit@redhat.com>
---
v3:
* add aiocontext lock acquire/remove around bdrv_detach_aio_context
* typos and nitpicks
* remove patch 4: bdrv_child_try_change_aio_context: add transaction parameter

v2:
* remove transaction patch, and drain transactions
* re-add old AioContext lock/unlock, since it makes sense to have it
* typos in commit message
* various cleanups in block-backend callbacks
* use hash map instead of glist when marking visited nodes
* 2 more additional patches, getting rid of
  bdrv_try_set_aio_context and bdrv_child_try_change_aio_context

Emanuele Giuseppe Esposito (10):
  block.c: assert bs->aio_context is written under BQL and drains
  block: use transactions as a replacement of ->{can_}set_aio_context()
  bdrv_change_aio_context: use hash table instead of list of visited
    nodes
  blockjob: implement .change_aio_ctx in child_job
  block: implement .change_aio_ctx in child_of_bds
  block-backend: implement .change_aio_ctx in child_root
  block: use the new _change_ API instead of _can_set_ and _set_
  block: remove all unused ->can_set_aio_ctx and ->set_aio_ctx callbacks
  block: rename bdrv_child_try_change_aio_context in
    bdrv_try_change_aio_context
  block: remove bdrv_try_set_aio_context and replace it with
    bdrv_try_change_aio_context

 block.c                            | 363 ++++++++++++++++-------------
 block/block-backend.c              |  74 +++---
 block/export/export.c              |   2 +-
 blockdev.c                         |  22 +-
 blockjob.c                         |  50 ++--
 docs/devel/multiple-iothreads.txt  |   4 +-
 include/block/block-global-state.h |  15 +-
 include/block/block_int-common.h   |   6 +-
 job.c                              |   2 +-
 tests/unit/test-bdrv-drain.c       |   6 +-
 tests/unit/test-block-iothread.c   |  10 +-
 11 files changed, 309 insertions(+), 245 deletions(-)

-- 
2.31.1