Re: [Qemu-block] [PATCH v2] nbd/server: attach client channel to the export's AioContext

[John Snow]

On 9/20/19 2:12 PM, John Snow wrote:
> 
> 
> On 9/12/19 7:00 AM, Sergio Lopez wrote:
>> On creation, the export's AioContext is set to the same one as the
>> BlockBackend, while the AioContext in the client QIOChannel is left
>> untouched.
>>
>> As a result, when using data-plane, nbd_client_receive_next_request()
>> schedules coroutines in the IOThread AioContext, while the client's
>> QIOChannel is serviced from the main_loop, potentially triggering the
>> assertion at qio_channel_restart_[read|write].
>>
>> To fix this, as soon we have the export corresponding to the client,
>> we call qio_channel_attach_aio_context() to attach the QIOChannel
>> context to the export's AioContext. This matches with the logic at
>> blk_aio_attached().
>>
>> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1748253
>> Signed-off-by: Sergio Lopez <address@hidden>
>> ---
>> Changelog
>>
>> v2:
>>  - Attach the channel once after negotiation completes, avoiding
>>    duplication. (thanks Kevin Wolf).
>> ---
>>  nbd/server.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/nbd/server.c b/nbd/server.c
>> index 28c3c8be85..31d624e146 100644
>> --- a/nbd/server.c
>> +++ b/nbd/server.c
>> @@ -1297,6 +1297,11 @@ static coroutine_fn int nbd_negotiate(NBDClient 
>> *client, Error **errp)
>>          return ret;
>>      }
>>  
>> +    /* Attach the channel to the same AioContext as the export */
>> +    if (client->exp && client->exp->ctx) {
>> +        qio_channel_attach_aio_context(client->ioc, client->exp->ctx);
>> +    }
>> +
>>      assert(!client->optlen);
>>      trace_nbd_negotiate_success();
>>  
>>
> 
> I assume this patch has been superseded by Eric's later patches?

Nevermind -- my filtering got messed up slightly and I missed the
followup. I see that Eric staged this.

--js