Re: [Qemu-devel] [PATCH v7 4/6] qcow2: Add support for ImageInfoSpecific

[Kevin Wolf <kwolf@redhat.com>]

Am 02.10.2013 um 10:39 hat Max Reitz geschrieben:
> Add a new ImageInfoSpecificQCow2 type as a subtype of ImageInfoSpecific.
> This contains the compatibility level as a string and an optional
> lazy_refcounts boolean (optional means mandatory for compat >= 1.1 and
> not available for compat == 0.10).
> 
> Also, add qcow2_get_specific_info, which returns this information.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
>  block/qcow2.c    | 19 +++++++++++++++++++
>  qapi-schema.json | 16 ++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 4a9888c..396650d 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1810,6 +1810,24 @@ static int qcow2_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
>      return 0;
>  }
>  
> +static ImageInfoSpecific *qcow2_get_specific_info(BlockDriverState *bs)
> +{
> +    BDRVQcowState *s = bs->opaque;
> +    ImageInfoSpecific *spec_info = g_new0(ImageInfoSpecific, 1);
> +
> +    spec_info->kind = IMAGE_INFO_SPECIFIC_KIND_QCOW2;
> +    spec_info->qcow2 = g_new0(ImageInfoSpecificQCow2, 1);
> +    if (s->qcow_version == 2) {
> +        spec_info->qcow2->compat = g_strdup("0.10");
> +    } else if (s->qcow_version == 3) {
> +        spec_info->qcow2->compat = g_strdup("1.1");
> +        spec_info->qcow2->lazy_refcounts = s->use_lazy_refcounts;

If this function gets reused in a running qemu instance, e.g. from the
monitor, I think the semantics we'd want it to have is to describe the
image file, not the current options (which may have been modified on the
command line or using other monitor commands).

By checking s->compatible_features instead of s->use_lazy_refcounts you
would always return this information.

(Also, how could you leave out this opportunity to use compound
literals?! ;-))

> +        spec_info->qcow2->has_lazy_refcounts = true;
> +    }
> +
> +    return spec_info;
> +}

Kevin