Re: [Qemu-block] [Qemu-devel] Restoring bitmaps after failed/cancelled migration

[Vladimir Sementsov-Ogievskiy]

12.05.2018 00:23, John Snow wrote:
> On 04/18/2018 10:00 AM, Vladimir Sementsov-Ogievskiy wrote:
> > Hi all.
> >
> > We now have the following problem:
> >
> > If dirty-bitmaps migration capability is enabled, persistance flag is
> > dropped for all migrated bitmaps, to prevent their storing to the
> > storage on inactivate. It works ok, persistence itself is migrated
> > through the migration channel. But on source, bitmaps becomes not
> > persistent, so if we, for some reasons, want to continue using source
> > vm, we'll lose bitmaps on stop/start.
> Sorry for not following along more carefully, which kind of migration
> are we talking about in this case?

Any migration with dirty-bitmaps capability enabled..

> > It's simple to fix it: just make bitmaps persistent again on invalidate
> > [1].. But I have some questions.
> >
> > 1. What are possible cases? I think about the following:
> >
> > a. migration cancel or fail, then invalidate
> > b. migration success, then qmp cont => invalidate
> > c. migration success, then stop/start (there was no invalidate, so [1]
> > will not work)
> >
> >
> > 2. Is it safe at all, saving bitmaps after inactivate, even without
> > persistence?
> >
> > Inactive disk implies, that it may be changed by somebody other, isn't
> > it? Is it possible, that target will change the disk, and then we return
> > control to the source? In this case bitmaps will be invalid. So, should
> > not we drop all the bitmaps on inactivate?


--
Best regards,
Vladimir