On Thu, Aug 21, 2014 at 07:56:55PM +0800, Fam Zheng wrote:
> diff --git a/block.c b/block.c
> index 1cc8926..1860e4b 100644
> --- a/block.c
> +++ b/block.c
> @@ -4750,9 +4750,14 @@ static void bdrv_aio_co_cancel_em(BlockDriverAIOCB *blockacb)
>      }
>  }
>  
> +static void bdrv_aio_co_cancel_em_async(BlockDriverAIOCB *blockacb)
> +{
> +}

Please include a comment to explain why this function body is empty:

/* Do nothing, let caller wait for the request to complete */