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Re: [PATCH v8 33/34] qcow2: Assert that expand_zero_clusters_in_l1() doe
From: |
Alberto Garcia |
Subject: |
Re: [PATCH v8 33/34] qcow2: Assert that expand_zero_clusters_in_l1() does not support subclusters |
Date: |
Thu, 11 Jun 2020 15:24:30 +0200 |
User-agent: |
Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) |
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
- [PATCH v8 11/34] qcow2: Add offset_into_subcluster() and size_to_subclusters(), (continued)
- [PATCH v8 11/34] qcow2: Add offset_into_subcluster() and size_to_subclusters(), Alberto Garcia, 2020/06/10
- [PATCH v8 15/34] qcow2: Add qcow2_get_subcluster_range_type(), Alberto Garcia, 2020/06/10
- [PATCH v8 03/34] qcow2: Add calculate_l2_meta(), Alberto Garcia, 2020/06/10
- [PATCH v8 06/34] qcow2: Add get_l2_entry() and set_l2_entry(), Alberto Garcia, 2020/06/10
- [PATCH v8 22/34] qcow2: Add subcluster support to zero_in_l2_slice(), Alberto Garcia, 2020/06/10
- [PATCH v8 01/34] qcow2: Make Qcow2AioTask store the full host offset, Alberto Garcia, 2020/06/10
- [PATCH v8 04/34] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), Alberto Garcia, 2020/06/10
- [PATCH v8 12/34] qcow2: Add l2_entry_size(), Alberto Garcia, 2020/06/10
- [PATCH v8 33/34] qcow2: Assert that expand_zero_clusters_in_l1() does not support subclusters, Alberto Garcia, 2020/06/10
- [PATCH v8 30/34] qcow2: Add prealloc field to QCowL2Meta, Alberto Garcia, 2020/06/10
- [PATCH v8 27/34] qcow2: Add subcluster support to handle_alloc_space(), Alberto Garcia, 2020/06/10
- [PATCH v8 32/34] qcow2: Allow preallocation and backing files if extended_l2 is set, Alberto Garcia, 2020/06/10
- [PATCH v8 29/34] qcow2: Add subcluster support to qcow2_measure(), Alberto Garcia, 2020/06/10
- [PATCH v8 20/34] qcow2: Add subcluster support to calculate_l2_meta(), Alberto Garcia, 2020/06/10
- [PATCH v8 07/34] qcow2: Document the Extended L2 Entries feature, Alberto Garcia, 2020/06/10
- [PATCH v8 02/34] qcow2: Convert qcow2_get_cluster_offset() into qcow2_get_host_offset(), Alberto Garcia, 2020/06/10