Vladimir Sementsov-Ogievskiy <[email protected]> writes:
> Add a parameter that enables discard-after-copy. That is mostly useful
> in "push backup with fleecing" scheme, when source is snapshot-access
> format driver node, based on copy-before-write filter snapshot-access
> API:
>
> [guest] [snapshot-access] ~~ blockdev-backup ~~> [backup target]
> | |
> | root | file
> v v
> [copy-before-write]
> | |
> | file | target
> v v
> [active disk] [temp.img]
>
> In this case discard-after-copy does two things:
>
> - discard data in temp.img to save disk space
> - avoid further copy-before-write operation in discarded area
>
> Note that we have to declare WRITE permission on source in
> copy-before-write filter, for discard to work. Still we can't take it
> unconditionally, as it will break normal backup from RO source. So, we
> have to add a parameter and pass it thorough bdrv_open flags.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
> Reviewed-by: Fiona Ebner <[email protected]>
> Tested-by: Fiona Ebner <[email protected]>
[...]
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 1874f880a8..2ef52ae9a7 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -1610,6 +1610,9 @@
> # node specified by @drive. If this option is not given, a node
> # name is autogenerated. (Since: 4.2)
> #
> +# @discard-source: Discard blocks on source which are already copied
"have been copied"?
> +# to the target. (Since 9.1)
> +#
> # @x-perf: Performance options. (Since 6.0)
> #
> # Features:
> @@ -1631,6 +1634,7 @@
> '*on-target-error': 'BlockdevOnError',
> '*auto-finalize': 'bool', '*auto-dismiss': 'bool',
> '*filter-node-name': 'str',
> + '*discard-source': 'bool',
> '*x-perf': { 'type': 'BackupPerf',
> 'features': [ 'unstable' ] } } }
QAPI schema
Acked-by: Markus Armbruster <[email protected]>
