Re: [PATCH v2 09/10] block: Convert qmp_query_block() to coroutine_fn

[Fabiano Rosas <farosas@suse.de>]

Hanna Czenczek <hreitz@redhat.com> writes:

> On 09.06.23 22:19, Fabiano Rosas wrote:
>> This is another caller of bdrv_get_allocated_file_size() that needs to
>> be converted to a coroutine because that function will be made
>> asynchronous when called (indirectly) from the QMP dispatcher.
>>
>> This QMP command is a candidate because it calls bdrv_do_query_node_info(),
>> which in turn calls bdrv_get_allocated_file_size().
>>
>> We've determined bdrv_do_query_node_info() to be coroutine-safe (see
>> previous commits), so we can just put this QMP command in a coroutine.
>>
>> Since qmp_query_block() now expects to run in a coroutine, its callers
>> need to be converted as well. Convert hmp_info_block(), which calls
>> only coroutine-safe code, including qmp_query_named_block_nodes()
>> which has been converted to coroutine in the previous patches.
>>
>> Now that all callers of bdrv_[co_]block_device_info() are using the
>> coroutine version, a few things happen:
>>
>>   - we can return to using bdrv_block_device_info() without a wrapper;
>>
>>   - bdrv_get_allocated_file_size() can stop being mixed;
>>
>>   - bdrv_co_get_allocated_file_size() needs to be put under the graph
>>     lock because it is being called wthout the wrapper;
>>
>>   - bdrv_do_query_node_info() doesn't need to acquire the AioContext
>>     because it doesn't call aio_poll anymore;
>>
>> Signed-off-by: Fabiano Rosas <farosas@suse.de>
>> ---
>>   block.c                        |  2 +-
>>   block/monitor/block-hmp-cmds.c |  2 +-
>>   block/qapi.c                   | 18 +++++++++---------
>>   hmp-commands-info.hx           |  1 +
>>   include/block/block-hmp-cmds.h |  2 +-
>>   include/block/block-io.h       |  2 +-
>>   include/block/qapi.h           | 12 ++++--------
>>   qapi/block-core.json           |  2 +-
>>   8 files changed, 19 insertions(+), 22 deletions(-)
>
> After this series has been sent, we got some usages of 
> GRAPH_RDLOCK_GUARD_MAINLOOP() that no longer fit with this patch – I’ve 
> also mentioned one case on patch 7, not yet realizing that this was a 
> new thing.  Those must now be fixed (e.g. in qmp_query_block(), or in 
> bdrv_snapshot_list()), or they’ll crash.

Hi, thanks for the reviews!

Yes, there's been a lot of changes since this series was sent. I'll
rebase it and re-evaluate. Stefan just sent an AioContext series which
will probably help bring the complexity of down for this series. Let's
see how it goes.