formatstorage: Document qcow2 default version change

Based on discussion after commit f432114d9c was pushed it was pointed
out that the documentation still mentions the older version.

Fix the documentation to state the new version and introduce ambiguity
for future updates.

Fixes: f432114d9cf507a4047aa9dc1344b1c13356db08
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>

diff --git a/docs/formatstorage.rst b/docs/formatstorage.rst
index 86e167d9cb0e5b3f7826a245131090c97679bbca..9d9a4143eb6df84e59b5875c3f0e2478671c7765 100644 (file)
--- a/docs/formatstorage.rst
+++ b/docs/formatstorage.rst
@@ -700,10 +700,15 @@ host filesystem. It can contain the following child elements:
    Encryption <formatstorageencryption.html>`__ page for more information.
 ``compat``
    Specify compatibility level. So far, this is only used for ``type='qcow2'``
-   volumes. Valid values are ``0.10`` and ``1.1`` so far, specifying QEMU
-   version the images should be compatible with. If the ``feature`` element is
-   present, 1.1 is used. :since:`Since 1.1.0` If omitted, 0.10 is used.
-   :since:`Since 1.1.2`
+   volumes. Valid values are ``0.10`` (QCOW2 v2) and ``1.1`` (QCOW2 v3) so far.
+   The values were meant to specify QEMU version the images should be compatible
+   with.
+
+   The default, if the ``feature`` element is present is ``1.1``. :since:`Since 1.1.0`
+   If ``feature`` is not present, ``0.10`` was used :since:`Since 1.1.2` and
+   :since:`Since 10.2.0` ``1.1`` is used as it's the default of ``qemu-img``.
+
+   Any tool depending on a specific version should specify this field explicitly.
 ``nocow``
    Turn off COW of the newly created volume. So far, this is only valid for a
    file image in btrfs file system. It will improve performance when the file