Re: [PATCH v4 07/30] qcow2: Document the Extended L2 Entries feature

[Vladimir Sementsov-Ogievskiy]

14.04.2020 19:30, Alberto Garcia wrote:
> On Tue 14 Apr 2020 06:19:18 PM CEST, Vladimir Sementsov-Ogievskiy 
> <address@hidden> wrote:
> > > > It still may cache information about zeroed subclusters: gives more
> > > > detailed block-status. But we should mention somehow external
> > > > files. Hm. not only for raw external files, but it is documented that
> > > > cluster can't be unallocated when an external data file is used.
> > >
> > > What do you mean by "cluster can't be unallocated" ?
> >
> > I mean this sentence from qcow2.txt:
> >
> >                      "The offset may only be 0 with
> >                       bit 63 set (indicating a host cluster offset of 0) when an
> >                       external data file is used."
> >
> > In other words, cluster can't be unallocated with data file in use.
>
> I still don't follow... clusters can be unallocated, and when you create
> a new image they are indeed unallocated.

with external data file? Than we probably need to fix spec..

unallocated mean that offset is 0, and bit 63 is unset. But this can't be when 
and exernal data file is used, accordingly to the spec.

Or what am I missing?

--
Best regards,
Vladimir