On 03/10/2016 10:49 AM, Changlong Xie wrote:
From: Wen Congyang <we...@cn.fujitsu.com>

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

Signed-off-by: Wen Congyang <we...@cn.fujitsu.com>
Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
Signed-off-by: Gonglei <arei.gong...@huawei.com>
Signed-off-by: Changlong Xie <xiecl.f...@cn.fujitsu.com>
Reviewed-by: Max Reitz <mre...@redhat.com>
---
  blockdev.c           | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
  qapi/block-core.json | 32 ++++++++++++++++++++++++++++++
  qmp-commands.hx      | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++
  3 files changed, 141 insertions(+)

diff --git a/blockdev.c b/blockdev.c
index 0f20c65..435631e 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -4017,6 +4017,61 @@ out:
      aio_context_release(aio_context);
  }

+static BdrvChild *bdrv_find_child(BlockDriverState *parent_bs,
+                                  const char *child_name)
+{
+    BdrvChild *child;
+
+    QLIST_FOREACH(child, &parent_bs->children, next) {
+        if (strcmp(child->name, child_name) == 0) {
+            return child;
+        }
+    }
+
+    return NULL;
+}
+
+void qmp_x_blockdev_change(const char *parent, bool has_child,
+                           const char *child, bool has_node,
+                           const char *node, Error **errp)
+{
+    BlockDriverState *parent_bs, *new_bs = NULL;
+    BdrvChild *p_child;
+
+    parent_bs = bdrv_lookup_bs(parent, parent, errp);
+    if (!parent_bs) {
+        return;
+    }
+
+    if (has_child == has_node) {
+        if (has_child) {
+            error_setg(errp, "The parameters child and node are in conflict");
+        } else {
+            error_setg(errp, "Either child or node must be specified");
+        }
+        return;
+    }
+
+    if (has_child) {
+        p_child = bdrv_find_child(parent_bs, child);
+        if (!p_child) {
+            error_setg(errp, "Node '%s' does not have child '%s'",
+                       parent, child);
+            return;
+        }
+        bdrv_del_child(parent_bs, p_child, errp);
+    }
+
+    if (has_node) {
+        new_bs = bdrv_find_node(node);
+        if (!new_bs) {
+            error_setg(errp, "Node '%s' not found", node);
+            return;
+        }
+        bdrv_add_child(parent_bs, new_bs, errp);
+    }
+}
+
  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 9bf1b22..bc3fd0b 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2548,3 +2548,35 @@
  ##
  { 'command': 'block-set-write-threshold',
    'data': { 'node-name': 'str', 'write-threshold': 'uint64' } }
+
+##
+# @x-blockdev-change
+#
+# Dynamically reconfigure the block driver state graph. It can be used
+# to add, remove, insert or replace a graph node. Currently only the
+# Quorum driver implements this feature to add or remove its child. This
+# is useful to fix a broken quorum child.
+#
+# If @node is specified, it will be inserted under @parent. @child
+# may not be specified in this case. If both @parent and @child are
+# specified but @node is not, @child will be detached from @parent.
+#
+# @parent: the id or name of the parent node.
+#
+# @child: #optional the name of a child under the given parent node.
+#
+# @node: #optional the name of the node that will be added.
+#
+# Note: this command is experimental, and its API is not stable. It
+# does not support all kinds of operations, all kinds of children, nor
+# all block drivers.
+#
+# Warning: The data in a new quorum child MUST be consistent with that of
+# the rest of the array.
+#
+# Since: 2.6
+##
+{ 'command': 'x-blockdev-change',
+  'data' : { 'parent': 'str',
+             '*child': 'str',
+             '*node': 'str' } }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index b629673..2a55135 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -4398,6 +4398,60 @@ Example:
  EQMP

      {
+        .name       = "x-blockdev-change",
+        .args_type  = "parent:B,child:B?,node:B?",
+        .mhandler.cmd_new = qmp_marshal_x_blockdev_change,
+    },
+
+SQMP
+x-blockdev-change
+-----------------
+
+Dynamically reconfigure the block driver state graph. It can be used
+to add, remove, insert or replace a graph node. Currently only the
+Quorum driver implements this feature to add or remove its child. This
+is useful to fix a broken quorum child.
+
+If @node is specified, it will be inserted under @parent. @child
+may not be specified in this case. If both @parent and @child are
+specified but @node is not, @child will be detached from @parent.
+
+Arguments:
+- "parent": the id or name of the parent node (json-string)
+- "child": the name of a child under the given parent node (json-string, 
optional)
+- "node": the name of the node that will be added (json-string, optional)
+
+Note: this command is experimental, and not a stable API. It doesn't
+support all kinds of operations, all kinds of children, nor all block
+drivers.
+
+Warning: The data in a new quorum child MUST be consistent with that of
+the rest of the array.
+
+Example:
+
+Add a new node to a quorum
+-> { "execute": "blockdev-add",
+    "arguments": { "options": { "driver": "raw",
+                                "node-name": "new_node",
+                                "id": "test_new_node",

Since f21d96d04 block: Use BdrvChild in BlockBackend, if we want to create a node without BB, we should not pass " "id": "test_new_node" ",
will fix in next version.

Thanks
        -Xie
+                                "file": { "driver": "file",
+                                          "filename": "test.raw" } } } }
+<- { "return": {} }
+-> { "execute": "x-blockdev-change",
+    "arguments": { "parent": "disk1",
+                   "node": "new_node" } }
+<- { "return": {} }
+
+Delete a quorum's node
+-> { "execute": "x-blockdev-change",
+    "arguments": { "parent": "disk1",
+                   "child": "children.1" } }
+<- { "return": {} }
+
+EQMP
+
+    {
          .name       = "query-named-block-nodes",
          .args_type  = "",
          .mhandler.cmd_new = qmp_marshal_query_named_block_nodes,




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