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

[Vladimir Sementsov-Ogievskiy]

14.04.2020 17:50, Alberto Garcia wrote:
> On Fri 10 Apr 2020 11:29:59 AM CEST, Vladimir Sementsov-Ogievskiy wrote:
> > > Hmm - raw external files are incompatible with backing files. Should
> > > we also document that extended L2 entries are incompatible with raw
> > > external files? (The text here reminded me about it, but it would be
> > > the text earlier at the incompatible feature bits that we edit if we
> > > want that additional restriction; compare to the restriction in the
> > > autoclear bit 1). After all, when raw external file is enabled, the
> > > entire image is allocated, at which point subclusters don't make much
> > > sense.
> > 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.

--
Best regards,
Vladimir