Am 12.10.2015 um 16:27 hat Paolo Bonzini geschrieben:
>
>
> On 12/10/2015 13:50, Fam Zheng wrote:
> > +void bdrv_drained_begin(BlockDriverState *bs)
> > +{
> > + if (bs->quiesce_counter++) {
> > + return;
> > + }
> > + aio_disable_external(bdrv_get_aio_context(bs));
> > + bdrv_drain(bs);
> > +}
>
> I think bdrv_drain should be called unconditionally, i.e. before the
> "if". This should also solve Kevin's doubt about new allocating write
> request reenabling the timer: any write request from the drained section
> happens normally, until you get a nested drain request and then the
> callback completes the requests.
This would mean that once you've sent an I/O request inside a drain
section, you have to expect that more internal I/O might be going on
after the request has completed. If you don't want this, you have to
issue another bdrv_drain() or use a nested bdrv_drained_begin/end()
section.
Sounds reasonable enough to me, but I guess this should be explicitly
documented.
Kevin
