Re: [PATCH v2 1/2] block: commit: Allow users to request only format driver names in backing file format

[Peter Krempa]

On Thu, Nov 30, 2023 at 13:24:18 -0600, Eric Blake wrote:
> On Thu, Nov 30, 2023 at 05:06:03PM +0100, Peter Krempa wrote:
> > Introduce a new flag 'backing_file_format_no_protocol' for the
> > block-commit QMP command which instructs the internals to use 'raw'
> > instead of the protocol driver in case when a image is used without a
> > dummy 'raw' wrapper.
> > 
> > The flag is designed such that it can be always asserted by management
> > tools even when there isn't any update to backing files.
> > 
> > The flag will be used by libvirt so that the backing images still
> > reference the proper format even when libvirt will stop using the dummy
> > raw driver (raw driver with no other config). Libvirt needs this so that
> > the images stay compatible with older libvirt versions which didn't
> > expect that a protocol driver name can appear in the backing file format
> > field.
> > 
> > Signed-off-by: Peter Krempa <pkrempa@redhat.com>
> > Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> > ---
> 
> > +++ b/qapi/block-core.json
> > @@ -1810,6 +1810,14 @@
> >  #     Care should be taken when specifying the string, to specify a
> >  #     valid filename or protocol.  (Since 2.1)
> >  #
> > +# @backing-file-format-no-protocol: If true always use a 'format' driver 
> > name
> > +#     for the 'backing file format' field if updating the image header of 
> > the
> > +#     overlay of 'top'. Otherwise the real name of the driver of the 
> > backing
> > +#     image may be used which may be a protocol driver.
> > +#
> > +#     Can be used also when no image header will be updated.
> > +#     (default: false; since: 9.0)


As I've previously stated, I don't really care about a name as long as I
don't have to keep re-sending,

> This is a long name.  What about:

But is the long name really a problem?

> @backing-mask-protocol: If true, replace any protocol mentioned in the
>     'backing file format' with 'raw', rather than storing the protocol
>     name as the backing format.  Can be used even when no image header
>     will be updated (default false; since 9.0).

Sounds okay to me. In the end, nobody will really see this as libvirt
will be using it internally