Re: [PATCH v8 33/34] qcow2: Assert that expand_zero_clusters_in_l1() does not support subclusters

[Alberto Garcia]

On Wed 10 Jun 2020 09:43:53 PM CEST, Eric Blake wrote:
> On 6/10/20 10:03 AM, Alberto Garcia wrote:
>> This function is only used by qcow2_expand_zero_clusters() to
>> downgrade a qcow2 image to a previous version. It is however not
>> possible to downgrade an image with extended L2 entries because older
>> versions of qcow2 do not have this feature.
>
> Well, it _is_ possible, but it would involve rewriting the entire
> L1/L2 tables (including all internal snapshots)

Right :-) Let's try this way:

    This function is only used by qcow2_expand_zero_clusters() to
    downgrade a qcow2 image to a previous version. This would require
    transforming all extended L2 entries into normal L2 entries but
    this is not a simple task and there are no plans to implement this
    at the moment.

Berto