Re: [Qemu-devel] [PATCH 2/2] Add file-posix-dynamic-auto-read-only feature

[Markus Armbruster]

Kevin Wolf <address@hidden> writes:

> auto-read-only=on changed its behaviour in file-posix for the 4.0
> release.

Commit hash, please.

>          This change cannot be detected through the usual mechanisms
> like schema introspection. Add a new feature to query-qemu-features to
> allow libvirt to detect the presence of the new behaviour.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  qapi/misc.json | 7 ++++++-
>  qmp.c          | 1 +
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/qapi/misc.json b/qapi/misc.json
> index d892f37633..df23c54a65 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -3058,10 +3058,15 @@
>  # Information about support for QEMU features that isn't available through
>  # schema introspection.
>  #
> +# @file-posix-dynamic-auto-read-only:
> +#   true if auto-read-only=on means that the image file is dynamically 
> reopened
> +#   read-only or read-write depending on whether any writers are attached to
> +#   the node.
> +#

The name @file-posix-dynamic-auto-read-only suggests the semantic change
of auto-read-only=on explained in the doc comment applies only to some
BlockDrivers (as a non-variant member of BlockdevOptions, auto-read-only
applies to all).  Which ones exactly?

>  # Since: 4.0
>  ##
>  { 'struct': 'QemuFeatures',
> -  'data': { } }
> +  'data': { 'file-posix-dynamic-auto-read-only': 'bool' } }
>  
>  ##
>  # @query-qemu-features:
> diff --git a/qmp.c b/qmp.c
> index 0aad533eca..2a887c1e7d 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -723,6 +723,7 @@ QemuFeatures *qmp_query_qemu_features(Error **errp)
>      QemuFeatures *caps = g_new(QemuFeatures, 1);
>  
>      *caps = (QemuFeatures) {
> +        .file_posix_dynamic_auto_read_only = true,
>      };
>  
>      return caps;

Running the command provides no additional information over schema
introspection.  Kind of contradicts "Information about support for QEMU
features that isn't available through schema introspection" :)