On Fri, 10/23 16:13, Stefan Hajnoczi wrote:
> On Fri, Oct 23, 2015 at 11:08:09AM +0800, Fam Zheng wrote:
> > +void bdrv_drained_begin(BlockDriverState *bs)
> > +{
> > + if (!bs->quiesce_counter++) {
> > + aio_disable_external(bdrv_get_aio_context(bs));
> > + }
> > + bdrv_drain(bs);
> > +}
> > +
> > +void bdrv_drained_end(BlockDriverState *bs)
> > +{
> > + assert(bs->quiesce_counter > 0);
> > + if (--bs->quiesce_counter > 0) {
> > + return;
> > + }
> > + aio_enable_external(bdrv_get_aio_context(bs));
> > +}
>
> Why is quiesce_counter necessary? Can't we just rely on AioContext's
> disable_external_cnt?
It was added because bdrv_drain was conditional in a previous version, so yes
it can now be dropped, but we lose the explcitness of the assertion in
bdrv_drained_end. I was thinking that more "assert(!bs->quiesce_counter)" can
be useful in blk_aio_read/write etc..
Fam
