Re: [Qemu-devel] [PATCH v3 18/25] rbd: use BlockDriverState's AioContext

[Paolo Bonzini <pbonzini@redhat.com>]

Il 09/05/2014 02:04, Josh Durgin ha scritto:
> On 05/08/2014 07:34 AM, Stefan Hajnoczi wrote:
>> Drop the assumption that we're using the main AioContext.  Convert
>> qemu_bh_new() to aio_bh_new() and qemu_aio_wait() to aio_poll().
>>
>> The .bdrv_detach_aio_context() and .bdrv_attach_aio_context() interfaces
>> are not needed since no fd handlers, timers, or BHs stay registered when
>> requests have been drained.
>>
>> Cc: Josh Durgin <josh.durgin@inktank.com>
>> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>> ---
>>   block/rbd.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/block/rbd.c b/block/rbd.c
>> index dbc79f4..41f7bdc 100644
>> --- a/block/rbd.c
>> +++ b/block/rbd.c
>> @@ -548,7 +548,7 @@ static void qemu_rbd_aio_cancel(BlockDriverAIOCB
>> *blockacb)
>>       acb->cancelled = 1;
>>
>>       while (acb->status == -EINPROGRESS) {
>> -        qemu_aio_wait();
>> +        aio_poll(bdrv_get_aio_context(acb->common.bs), true);
>>       }
>>
>>       qemu_aio_release(acb);
>> @@ -581,7 +581,8 @@ static void rbd_finish_aiocb(rbd_completion_t c,
>> RADOSCB *rcb)
>>       rcb->ret = rbd_aio_get_return_value(c);
>>       rbd_aio_release(c);
>>
>> -    acb->bh = qemu_bh_new(rbd_finish_bh, rcb);
>> +    acb->bh = aio_bh_new(bdrv_get_aio_context(acb->common.bs),
>> +                         rbd_finish_bh, rcb);
>>       qemu_bh_schedule(acb->bh);
>>   }
>
> Assuming bdrv_get_aio_context() continues to be safe to call from a
> non-qemu thread:
>
> Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

bdrv_get_aio_context()/bdrv_set_aio_context() are safe if called from 
the AioContext's own iothread.  This is the case here, in fact 
aio_bh_new has the same requirement (qemu_bh_schedule instead does not).

Paolo