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

[Wen Congyang]

The new QMP command name is x-blockdev-change. It justs for adding/removing
quorum's child now, and don't support all kinds of children, all kinds of
operations, nor all block drivers. So it is experimental now.

Signed-off-by: Wen Congyang <address@hidden>
Signed-off-by: zhanghailiang <address@hidden>
Signed-off-by: Gonglei <address@hidden>
---
 blockdev.c           | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 qapi/block-core.json | 40 +++++++++++++++++++++++++++
 qmp-commands.hx      | 50 ++++++++++++++++++++++++++++++++++
 3 files changed, 166 insertions(+)

diff --git a/blockdev.c b/blockdev.c
index 6c8cce4..72efe5d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3086,6 +3086,82 @@ fail:
     qmp_output_visitor_cleanup(ov);
 }
 
+void qmp_x_blockdev_change(ChangeOperation op, const char *parent,
+                           bool has_child, const char *child,
+                           bool has_new_node, const char *new_node,
+                           Error **errp)
+{
+    BlockDriverState *parent_bs, *child_bs, *new_bs;
+    Error *local_err = NULL;
+
+    parent_bs = bdrv_lookup_bs(parent, parent, &local_err);
+    if (!parent_bs) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    switch(op) {
+    case CHANGE_OPERATION_ADD:
+        if (has_child) {
+            error_setg(errp, "The operation %s doesn't support the parameter 
child",
+                       ChangeOperation_lookup[op]);
+            return;
+        }
+        if (!has_new_node) {
+            error_setg(errp, "The operation %s needs the parameter new_node",
+                       ChangeOperation_lookup[op]);
+            return;
+        }
+        break;
+    case CHANGE_OPERATION_DELETE:
+        if (has_new_node) {
+            error_setg(errp, "The operation %s doesn't support the parameter 
node",
+                       ChangeOperation_lookup[op]);
+            return;
+        }
+        if (!has_child) {
+            error_setg(errp, "The operation %s needs the parameter child",
+                       ChangeOperation_lookup[op]);
+            return;
+        }
+    default:
+        break;
+    }
+
+    if (has_child) {
+        child_bs = bdrv_find_node(child);
+        if (!child_bs) {
+            error_setg(errp, "Node '%s' not found", child);
+            return;
+        }
+    }
+
+    if (has_new_node) {
+        new_bs = bdrv_find_node(new_node);
+        if (!new_bs) {
+            error_setg(errp, "Node '%s' not found", new_node);
+            return;
+        }
+    }
+
+    switch(op) {
+    case CHANGE_OPERATION_ADD:
+        bdrv_add_child(parent_bs, new_bs, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+        }
+        break;
+    case CHANGE_OPERATION_DELETE:
+        bdrv_del_child(parent_bs, child_bs, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+        }
+        break;
+    default:
+        break;
+    }
+}
+
 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 bb2189e..361588f 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2114,3 +2114,43 @@
 ##
 { 'command': 'block-set-write-threshold',
   'data': { 'node-name': 'str', 'write-threshold': 'uint64' } }
+
+##
+# @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' ] }
+
+##
+# @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.
+#
+# @node: the new node-name which will be added.
+#
+# 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' } }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index d2ba800..ede7b71 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -3921,6 +3921,56 @@ Example (2):
 EQMP
 
     {
+        .name       = "x-blockdev-change",
+        .args_type  = "operation:s,parent:B,child:B?,node:B?",
+        .mhandler.cmd_new = qmp_marshal_x_blockdev_change,
+    },
+
+SQMP
+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.
+
+Arguments:
+- "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 delete
+- "node": the new node-name which will be added
+
+Note: this command is experimental, and not a stable API. It doesn't
+support all kinds of operations, all kindes of children, nor all block
+drivers.
+
+Example:
+
+Add a new quorum's node
+-> { "execute": blockdev-add",
+    "arguments": { "options": { "driver": "raw",
+                                "node-name": "new_node",
+                                "id": "test_new_node",
+                                "file": { "driver": "file",
+                                          "filename": "test.raw" } } } }
+<- { "return": {} }
+-> { "execute": "x-blockdev-change",
+    "arguments": { "operation": "add",
+                   "parent": "disk1",
+                   "node": "new_node" } }
+<- { "return": {} }
+
+Delete a quorum's node
+-> { "execute": "x-blockdev-change",
+    "arguments": { "operation": "delete",
+                   "parent": "disk1",
+                   "child": "new_node" } }
+<- { "return": {} }
+
+EQMP
+
+    {
         .name       = "query-named-block-nodes",
         .args_type  = "",
         .mhandler.cmd_new = qmp_marshal_query_named_block_nodes,
-- 
2.4.3