Re: [Qemu-devel] [PATCH v6 3/4] qmp: add monitor command to add/remove a child

[Kevin Wolf <kwolf@redhat.com>]

Am 16.10.2015 um 10:57 hat Wen Congyang geschrieben:
> +##
> +# @ChangeOperation:
> +#
> +# An enumeration of block device change operation.
> +#
> +# @add: Add a new block driver state to a existed block driver state.
> +#
> +# @delete: Delete a block driver state's child.
> +#
> +# Since: 2.5
> +##
> +{ 'enum': 'ChangeOperation',
> +  'data': [ 'add', 'delete' ] }

What's the advantage of this enum compared to separate QMP commands? The
way it is specified here, ChangeOperation is already implicit by whether
or not child and node are given.

> +##
> +# @x-blockdev-change
> +#
> +# Dynamic reconfigure the block driver state graph. It can be used to
> +# add, remove, insert, replace a block driver state. Currently only
> +# the Quorum driver implements this feature to add and remove its child.
> +# This is useful to fix a broken quorum child.
> +#
> +# @operation: the chanage operation. It can be add, delete.
> +#
> +# @parent: the id or node name of which node will be changed.
> +#
> +# @child: the child node-name which will be deleted.

#optional

Must be present for operation = delete, must not be present otherwise.

> +# @node: the new node-name which will be added.

#optional

Must be present for operation = add, must not be present otherwise.

> +#
> +# Note: this command is experimental, and not a stable API.
> +#
> +# Since: 2.5
> +##
> +{ 'command': 'x-blockdev-change',
> +  'data' : { 'operation': 'ChangeOperation',
> +             'parent': 'str',
> +             '*child': 'str',
> +             '*node': 'str' } }

Let me suggest this alternative:

{ 'command': 'x-blockdev-change',
  'data' : { 'parent': 'str',
             'child': 'str',
             '*node': 'str' } }

child doesn't describe a node name then, but a child name (adds a
dependency on my patches which add a name to BdrvChild, though).
Depending on whether node is given and whether the child already exists,
this may add, remove or replace a child.

Kevin