Re: [PATCH v2 2/2] backup: add minimum cluster size to performance options

[Markus Armbruster]

Fiona Ebner <f.ebner@proxmox.com> writes:

> In the context of backup fleecing, discarding the source will not work
> when the fleecing image has a larger granularity than the one used for
> block-copy operations (can happen if the backup target has smaller
> cluster size), because cbw_co_pdiscard_snapshot() will align down the
> discard requests and thus effectively ignore then.
>
> To make @discard-source work in such a scenario, allow specifying the
> minimum cluster size used for block-copy operations and thus in
> particular also the granularity for discard requests to the source.
>
> Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

[...]

> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 8fc0a4b234..f1219a9dfb 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -1551,11 +1551,16 @@
>  #     it should not be less than job cluster size which is calculated
>  #     as maximum of target image cluster size and 64k.  Default 0.
>  #
> +# @min-cluster-size: Minimum size of blocks used by copy-before-write
> +#     and background copy operations.  Has to be a power of 2.  No
> +#     effect if smaller than the maximum of the target's cluster size
> +#     and 64 KiB.  Default 0.  (Since 9.1)
> +#
>  # Since: 6.0
>  ##
>  { 'struct': 'BackupPerf',
> -  'data': { '*use-copy-range': 'bool',
> -            '*max-workers': 'int', '*max-chunk': 'int64' } }
> +  'data': { '*use-copy-range': 'bool', '*max-workers': 'int',
> +            '*max-chunk': 'int64', '*min-cluster-size': 'size' } }
>  
>  ##
>  # @BackupCommon:

QAPI schema
Acked-by: Markus Armbruster <armbru@redhat.com>