Re: [PATCH v1] block/raw-format: implement .bdrv_get_specific_info handler

[Kevin Wolf <kwolf@redhat.com>]

Am 07.07.2021 um 07:35 hat Or Ozeri geschrieben:
> When using the raw format, allow exposing specific info by the underlying storage.
> In particular, this will enable RBD images using the raw format to indicate
> a LUKS2 encrypted image in the output of qemu-img info.
> 
> Signed-off-by: Or Ozeri <oro@il.ibm.com>

This doesn't feel right because it would introduce an inconsistency
(drivers are supposed to return information about their layer, and all
drivers except raw would still do so) and therefore wouldn't even solve
the full problem: For non-raw images, the information isn't any less
useful, but it still wouldn't be available.

I believe the information is already available in QMP, using
query-named-block-nodes, because then you get a separate BlockDeviceInfo
(which contains ImageInfoSpecific) for each node, including the protocol
node.

So maybe what we need to do is change qemu-img to iterate the node chain
(possibly using bdrv_primary_bs()) and print the ImageInfoSpecific for
each layer if it's present, while indicating which part is for which
layer.

So the output could look like this:

...
Driver specific information (qcow2):
    compat: 0.10
    compression type: zlib
    refcount bits: 16
Driver specific information (rbd):
    encryption format: luks

Kevin