Re: block snapshot issue with RBD

[Kevin Wolf <kwolf@redhat.com>]

Am 29.05.2024 um 12:14 hat Fiona Ebner geschrieben:
> I bisected this issue to d3007d348a ("block: Fix crash when loading
> snapshot on inactive node").
> 
> > diff --git a/block/snapshot.c b/block/snapshot.c
> > index ec8cf4810b..c4d40e80dd 100644
> > --- a/block/snapshot.c
> > +++ b/block/snapshot.c
> > @@ -196,8 +196,10 @@ bdrv_snapshot_fallback(BlockDriverState *bs)
> >  int bdrv_can_snapshot(BlockDriverState *bs)
> >  {
> >      BlockDriver *drv = bs->drv;
> > +
> >      GLOBAL_STATE_CODE();
> > -    if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
> > +
> > +    if (!drv || !bdrv_is_inserted(bs) || !bdrv_is_writable(bs)) {
> >          return 0;
> >      }
> >  
> 
> So I guess the issue is that the blockdev is not writable when
> "postmigrate" state?

That makes sense. The error message really isn't great, but after
migration, the image is assumed to be owned by the destination, so we
can't use it any more. 'cont' basically asserts that the migration
failed and we can get ownership back. I don't think we can do without a
manual command reactivating the image on the source, but we could have
one that does this without resuming the VM.

Kevin