Re: [Qemu-block] [PATCH 1/5] block/dirty-bitmap: add recording and busy properties

[Eric Blake]

On 2/11/19 7:02 PM, John Snow wrote:
> The current API allows us to report a single status, which we've defined as:
> 
> Frozen: has a successor, treated as qmp_locked, may or may not be enabled.
> Locked: no successor, qmp_locked. may or may not be enabled.
> Disabled: Not frozen or locked, disabled.
> Active: Not frozen, locked, or disabled.
> 
> The problem is that both "Frozen" and "Locked" mean nearly the same thing,
> and that both of them do not intuit whether they are recording guest writes
> or not.
> 
> This patch deprecates that status field and introduces two orthogonal
> properties instead to replace it.
> ---

No S-o-b?


> +++ b/qapi/block-core.json
> @@ -455,7 +455,13 @@
>  #
>  # @granularity: granularity of the dirty bitmap in bytes (since 1.4)
>  #
> -# @status: current status of the dirty bitmap (since 2.4)
> +# @status: Deprecated in favor of @recording and @locked. (since 4.0)

I'd leave this one as (since 2.4). The deprecation clock is starting in
4.0, but the field has been present longer, and it is still obvious to
readers...

> +#
> +# @recording: true if the bitmap is recording new writes from the guest.
> +#             Replaces `active` status. (since 4.0)

...that the replacement fields are only usable in 4.0 and newer.

> +#
> +# @busy: true if the bitmap is in-use by some operation (NBD or jobs)
> +#        and cannot be modified via QMP right now. (since 4.0)
>  #
>  # @persistent: true if the bitmap will eventually be flushed to persistent
>  #              storage (since 4.0)
> @@ -464,6 +470,7 @@
>  ##
>  { 'struct': 'BlockDirtyInfo',
>    'data': {'*name': 'str', 'count': 'int', 'granularity': 'uint32',
> +           'recording': 'bool', 'busy': 'bool',
>             'status': 'DirtyBitmapStatus', 'persistent': 'bool' } }

The UI changes look reasonable.

No iotests coverage of "busy":true?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

signature.asc
Description: OpenPGP digital signature