Re: [Qemu-devel] [PATCH v3 4/5] qmp: add monitor command to add/remove a child

[Markus Armbruster]

Wen Congyang <address@hidden> writes:

> Signed-off-by: Wen Congyang <address@hidden>
> Signed-off-by: zhanghailiang <address@hidden>
> Signed-off-by: Gonglei <address@hidden>
> ---
>  blockdev.c           | 47 ++++++++++++++++++++++++++++++++++++++++++++++
>  qapi/block-core.json | 34 +++++++++++++++++++++++++++++++++
>  qmp-commands.hx      | 53 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 134 insertions(+)
>
> diff --git a/blockdev.c b/blockdev.c
> index bd47756..0a40607 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -3413,6 +3413,53 @@ fail:
>      qmp_output_visitor_cleanup(ov);
>  }
>  
> +void qmp_x_child_add(const char *parent, const char *child,
> +                     Error **errp)
> +{
> +    BlockDriverState *parent_bs, *child_bs;
> +    Error *local_err = NULL;
> +
> +    parent_bs = bdrv_lookup_bs(parent, parent, &local_err);
> +    if (!parent_bs) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +
> +    child_bs = bdrv_find_node(child);
> +    if (!child_bs) {
> +        error_setg(errp, "Node '%s' not found", child);
> +        return;
> +    }
> +
> +    bdrv_add_child(parent_bs, child_bs, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +    }
> +}
> +
> +void qmp_child_del(const char *parent, const char *child, Error **errp)
> +{
> +    BlockDriverState *parent_bs, *child_bs;
> +    Error *local_err = NULL;
> +
> +    parent_bs = bdrv_lookup_bs(parent, parent, &local_err);
> +    if (!parent_bs) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +
> +    child_bs = bdrv_find_node(child);
> +    if (!child_bs) {
> +        error_setg(errp, "Node '%s' not found", child);
> +        return;
> +    }
> +
> +    bdrv_del_child(parent_bs, child_bs, &local_err);
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +    }
> +}
> +
>  BlockJobInfoList *qmp_query_block_jobs(Error **errp)
>  {
>      BlockJobInfoList *head = NULL, **p_next = &head;
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index e68a59f..b959577 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -2272,3 +2272,37 @@
>  ##
>  { 'command': 'block-set-write-threshold',
>    'data': { 'node-name': 'str', 'write-threshold': 'uint64' } }
> +
> +##
> +# @x-child-add
> +#
> +# Add a new child to the parent BDS. Currently only the Quorum driver
> +# implements this feature. This is useful to fix a broken quorum child.
> +#
> +# @parent: graph node name or id which the child will be added to.
> +#
> +# @child: graph node name that will be added.
> +#
> +# Note: this command is experimental, and not a stable API.
> +#
> +# Since: 2.5
> +##
> +{ 'command': 'x-child-add',
> +  'data' : { 'parent': 'str', 'child': 'str' } }
> +
> +##
> +# @child-del
> +#
> +# Remove a child from the parent BDS. Currently only the Quorum driver
> +# implements this feature. This is useful to fix a broken quorum child.
> +# Note, you can't remove a child if it would bring the quorum below its
> +# threshold.
> +#
> +# @parent: graph node name or id from which the child will removed.
> +#
> +# @child: graph node name that will be removed.
> +#
> +# Since: 2.5
> +##
> +{ 'command': 'child-del',
> +  'data' : { 'parent': 'str', 'child': 'str' } }

Why is x-child-add experimental, but child-del isn't?  Please explain
both in the schema and in the commit message.

> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 495670b..139a23b 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -4053,6 +4053,59 @@ Example:
>  EQMP
>  
>      {
> +        .name       = "x-child-add",
> +        .args_type  = "parent:B,child:B",
> +        .mhandler.cmd_new = qmp_marshal_input_x_child_add,
> +    },
> +
> +SQMP
> +x-child-add
> +------------
> +
> +Add a child to a quorum node.
> +
> +Arguments:
> +
> +- "parent": the quorum's id or node name
> +- "child": the child node-name which will be added

Node name parameters are usually named node-name or, if there's more
than one, FOO-node-name.  Unless we want to abandon that convention,
this should therefore be node-name and child-node-name, or parent-node
name and child-node-name.

> +
> +Note: this command is experimental, and not a stable API.
> +
> +Example:
> +
> +-> { "execute": "x-child-add",
> +    "arguments": { "parent": "disk1", "child": "new_node" } }
> +<- { "return": {} }
> +
> +EQMP
> +
> +    {
> +        .name        = "child-del",

Documentation and schema have x-child-add, actual command is child-add.
Oops.

> +        .args_type   = "parent:B,child:B",
> +        .mhandler.cmd_new = qmp_marshal_input_child_del,
> +    },
> +
> +SQMP
> +child-del
> +------------
> +
> +Delete a child from a quorum node. It can be used to remove a broken
> +quorum child.
> +
> +Arguments:
> +
> +- "parent": the quorum's id or node name
> +- "child": the child node-name which will be removed

Same comment as on x-child-add's parameter names.

> +
> +Example:
> +
> +-> { "execute": "child-del",
> +    "arguments": { "parent": "disk1", "child": "new_node" } }
> +<- { "return": {} }
> +
> +EQMP
> +
> +    {
>          .name       = "query-named-block-nodes",
>          .args_type  = "",
>          .mhandler.cmd_new = qmp_marshal_input_query_named_block_nodes,