Re: [PATCH 1/9] block: call bdrv_co_drain_begin in a coroutine

[Paolo Bonzini]

On 11/3/22 14:41, Emanuele Giuseppe Esposito wrote:
> -    for (i = 0; i < bs->quiesce_counter; i++) {
> -        if (drv->bdrv_co_drain_begin) {
> -            drv->bdrv_co_drain_begin(bs);
> -        }
> +    if (drv->bdrv_co_drain_begin) {
> +        co = qemu_coroutine_create(bdrv_co_drain_begin, &dco);
> +        qemu_coroutine_enter(co);
> +        AIO_WAIT_WHILE(qemu_get_aio_context(), dco.ret == NOT_DONE);
>       }
>   

Alternatively there should be no reason for drv->bdrv_co_drain_begin to 
wait at this point, because the device does not have any active I/O.  So 
you could also assert that the coroutine is terminated after 
qemu_coroutine_enter(), i.e. that dco.ret != NOT_DONE.

Since you need to respin, perhaps put it the above in the commit message 
in case this needs a change in the future; however your patch is simple 
and should indeed work, so

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo