On Mon, Apr 10, 2017 at 11:05:32PM +0800, Fam Zheng wrote:
> v3: Respin the unmerged changes from v2 and include one new fix:
>
> (Yes, it is a big series for the last -rc, and I personally prefer the v2
> approach for the 4-9 part of the problem, which is much more mechanical.)
>
> - 1, 2 are redoing previous patch 4, using bdrv_parent_drained_begin/end.
> [Kevin]
> Also fix the ordering against aio_context_release. [Stefan]
> - 3 is unchanged from patch 6 in v2.
> - 4-9 are reworking of patch 5 following Paolo's suggestion, which allowed
> better patch split.
> - 10 is finding of a latent bug, which is revealed by patch 9.
>
> v2: - Drop patch 4 in v1. A second thought made me feel neither it nor Kevin's
> suggestion to move the BH process to bdrv_drain_recurse/BDRV_POLL_WHILE
> is a complete fix. So leave it for a separate patch.
> - Add rev-by to patches 1, 3, 4.
> - Split from patch 1 in v1 and add patch 2, for the new assertions. [Kevin]
> - Rewrite patch 5. Fix block job's co when a BDS is moved to a different
> aio context. [Kevin]
> - Add patch 6.
>
> Crashes are reported on dataplane devices when doing snapshot and commit under
> guest I/O.
>
> With this series, Ed's test case '176' now passes:
>
> https://github.com/skyportsystems/qemu-1/commits/eswierk-iotests-2.9
>
> Fam Zheng (10):
> block: Make bdrv_parent_drained_begin/end public
> block: Quiesce old aio context during bdrv_set_aio_context
> tests/block-job-txn: Don't start block job before adding to txn
> coroutine: Extract qemu_aio_coroutine_enter
> async: Introduce aio_co_enter and aio_co_enter_if_inactive
> block: Introduce bdrv_coroutine_enter and *_if_inactive
> blockjob: Use bdrv_coroutine_enter to start coroutine
> qemu-io-cmds: Use bdrv_coroutine_enter
> block: Use bdrv_coroutine_enter to start I/O coroutines
> block: Fix bdrv_co_flush early return
>
> block.c | 17 +++++++++++++++--
> block/block-backend.c | 4 ++--
> block/io.c | 34 ++++++++++++++++++----------------
> blockjob.c | 4 ++--
> include/block/aio.h | 18 ++++++++++++++++++
> include/block/block.h | 27 +++++++++++++++++++++++++++
> include/qemu/coroutine.h | 5 +++++
> qemu-io-cmds.c | 2 +-
> tests/qemu-iotests/109.out | 10 +++++-----
> tests/test-blockjob-txn.c | 6 +++++-
> util/async.c | 14 +++++++++++++-
> util/qemu-coroutine.c | 11 ++++++++---
> util/trace-events | 2 +-
> 13 files changed, 120 insertions(+), 34 deletions(-)
We need a fix for 2.9. Interactions between AioContexts, coroutines,
and blockjobs are complex and brittle. That is a pre-existing problem
though and hopefully we can simplify abstractions in 2.10.
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>