Re: [Qemu-block] [PATCH v3 2/9] block: Add auto-read-only option

[Eric Blake]

On 10/17/18 11:41 AM, Kevin Wolf wrote:
> If a management application builds the block graph node by node, the
> protocol layer doesn't inherit its read-only option from the format
> layer any more, so it must be set explicitly.

> The documentation for this option is consciously phrased in a way that
> allows QEMU to switch to a better model eventually: Instead of trying
> when the image is first opened, making the read-only flag dynamic and
> changing it automatically whenever the first BLK_PERM_WRITE user is
> attached or the last one is detached would be much more useful
> behaviour.

> +++ b/qapi/block-core.json
> @@ -3651,6 +3651,12 @@
>   #                 either generally or in certain configurations. In this case,
>   #                 the default value does not work and the option must be
>   #                 specified explicitly.
> +# @auto-read-only: if true and @read-only is false, QEMU may automatically
> +#                  decide not to open the image read-write as requested, but
> +#                  fall back to read-only instead (and switch between the modes
> +#                  later), e.g. depending on whether the image file is writable
> +#                  or whether a writing user is attached to the node
> +#                  (default: false, since 3.1)

Definitely better wording compared to v2.

Reviewed-by: Eric Blake <address@hidden>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org