qmp: Allow to take external snapshots on bs graphs node.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

blockdev.c

@@ -947,14 +947,22 @@ static void blockdev_do_action(int kind, void *data, Error **errp)
     qmp_transaction(&list, errp);
 }
 
-void qmp_blockdev_snapshot_sync(const char *device, const char *snapshot_file,
+void qmp_blockdev_snapshot_sync(bool has_device, const char *device,
+                                bool has_node_name, const char *node_name,
+                                const char *snapshot_file,
+                                bool has_snapshot_node_name,
+                                const char *snapshot_node_name,
                                 bool has_format, const char *format,
-                                bool has_mode, enum NewImageMode mode,
+                                bool has_mode, NewImageMode mode, Error **errp)
-                                Error **errp)
 {
     BlockdevSnapshot snapshot = {
+        .has_device = has_device,
         .device = (char *) device,
+        .has_node_name = has_node_name,
+        .node_name = (char *) node_name,
         .snapshot_file = (char *) snapshot_file,
+        .has_snapshot_node_name = has_snapshot_node_name,
+        .snapshot_node_name = (char *) snapshot_node_name,
         .has_format = has_format,
         .format = (char *) format,
         .has_mode = has_mode,
@@ -1192,8 +1200,14 @@ static void external_snapshot_prepare(BlkTransactionState *common,
 {
     BlockDriver *drv;
     int flags, ret;
+    QDict *options = NULL;
     Error *local_err = NULL;
+    bool has_device = false;
     const char *device;
+    bool has_node_name = false;
+    const char *node_name;
+    bool has_snapshot_node_name = false;
+    const char *snapshot_node_name;
     const char *new_image_file;
     const char *format = "qcow2";
     enum NewImageMode mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
@@ -1204,7 +1218,14 @@ static void external_snapshot_prepare(BlkTransactionState *common,
     /* get parameters */
     g_assert(action->kind == TRANSACTION_ACTION_KIND_BLOCKDEV_SNAPSHOT_SYNC);
 
+    has_device = action->blockdev_snapshot_sync->has_device;
     device = action->blockdev_snapshot_sync->device;
+    has_node_name = action->blockdev_snapshot_sync->has_node_name;
+    node_name = action->blockdev_snapshot_sync->node_name;
+    has_snapshot_node_name =
+        action->blockdev_snapshot_sync->has_snapshot_node_name;
+    snapshot_node_name = action->blockdev_snapshot_sync->snapshot_node_name;
+
     new_image_file = action->blockdev_snapshot_sync->snapshot_file;
     if (action->blockdev_snapshot_sync->has_format) {
         format = action->blockdev_snapshot_sync->format;
@@ -1220,9 +1241,21 @@ static void external_snapshot_prepare(BlkTransactionState *common,
         return;
     }
 
-    state->old_bs = bdrv_find(device);
+    state->old_bs = bdrv_lookup_bs(has_device ? device : NULL,
-    if (!state->old_bs) {
+                                   has_node_name ? node_name : NULL,
-        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+                                   &local_err);
+    if (error_is_set(&local_err)) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    if (has_node_name && !has_snapshot_node_name) {
+        error_setg(errp, "New snapshot node name missing");
+        return;
+    }
+
+    if (has_snapshot_node_name && bdrv_find_node(snapshot_node_name)) {
+        error_setg(errp, "New snapshot node name already existing");
         return;
     }
 
@@ -1262,15 +1295,23 @@ static void external_snapshot_prepare(BlkTransactionState *common,
         }
     }
 
+    if (has_snapshot_node_name) {
+        options = qdict_new();
+        qdict_put(options, "node-name",
+                  qstring_from_str(snapshot_node_name));
+    }
+
     /* We will manually add the backing_hd field to the bs later */
     state->new_bs = bdrv_new("");
     /* TODO Inherit bs->options or only take explicit options with an
      * extended QMP command? */
-    ret = bdrv_open(state->new_bs, new_image_file, NULL,
+    ret = bdrv_open(state->new_bs, new_image_file, options,
                     flags | BDRV_O_NO_BACKING, drv, &local_err);
     if (ret != 0) {
         error_propagate(errp, local_err);
     }
+
+    QDECREF(options);
 }
 
 static void external_snapshot_commit(BlkTransactionState *common)

hmp.c

@@ -972,7 +972,9 @@ void hmp_snapshot_blkdev(Monitor *mon, const QDict *qdict)
     }
 
     mode = reuse ? NEW_IMAGE_MODE_EXISTING : NEW_IMAGE_MODE_ABSOLUTE_PATHS;
-    qmp_blockdev_snapshot_sync(device, filename, !!format, format,
+    qmp_blockdev_snapshot_sync(true, device, false, NULL,
+                               filename, false, NULL,
+                               !!format, format,
                                true, mode, &errp);
     hmp_handle_error(mon, &errp);
 }

qapi-schema.json

@@ -1761,18 +1761,25 @@
 ##
 # @BlockdevSnapshot
 #
-# @device:  the name of the device to generate the snapshot from.
+# Either @device or @node-name must be set but not both.
+#
+# @device: #optional the name of the device to generate the snapshot from.
+#
+# @node-name: #optional graph node name to generate the snapshot from (Since 2.0)
 #
 # @snapshot-file: the target of the new image. A new file will be created.
 #
+# @snapshot-node-name: #optional the graph node name of the new image (Since 2.0)
+#
 # @format: #optional the format of the snapshot image, default is 'qcow2'.
 #
 # @mode: #optional whether and how QEMU should create a new image, default is
 #        'absolute-paths'.
 ##
 { 'type': 'BlockdevSnapshot',
-  'data': { 'device': 'str', 'snapshot-file': 'str', '*format': 'str',
+  'data': { '*device': 'str', '*node-name': 'str',
-            '*mode': 'NewImageMode' } }
+            'snapshot-file': 'str', '*snapshot-node-name': 'str',
+            '*format': 'str', '*mode': 'NewImageMode' } }
 
 ##
 # @BlockdevSnapshotInternal

qmp-commands.hx

@@ -1089,7 +1089,9 @@ actions array:
     - "data": a dictionary.  The contents depend on the value
       of "type".  When "type" is "blockdev-snapshot-sync":
       - "device": device name to snapshot (json-string)
+      - "node-name": graph node name to snapshot (json-string)
       - "snapshot-file": name of new image file (json-string)
+      - "snapshot-node-name": graph node name of the new snapshot (json-string)
       - "format": format of new image (json-string, optional)
       - "mode": whether and how QEMU should create the snapshot file
         (NewImageMode, optional, default "absolute-paths")
@@ -1104,6 +1106,11 @@ Example:
          { 'type': 'blockdev-snapshot-sync', 'data' : { "device": "ide-hd0",
                                          "snapshot-file": "/some/place/my-image",
                                          "format": "qcow2" } },
+         { 'type': 'blockdev-snapshot-sync', 'data' : { "node-name": "myfile",
+                                         "snapshot-file": "/some/place/my-image2",
+                                         "snapshot-node-name": "node3432",
+                                         "mode": "existing",
+                                         "format": "qcow2" } },
          { 'type': 'blockdev-snapshot-sync', 'data' : { "device": "ide-hd1",
                                          "snapshot-file": "/some/place/my-image2",
                                          "mode": "existing",
@@ -1117,7 +1124,7 @@ EQMP
 
     {
         .name       = "blockdev-snapshot-sync",
-        .args_type  = "device:B,snapshot-file:s,format:s?,mode:s?",
+        .args_type  = "device:s?,node-name:s?,snapshot-file:s,snapshot-node-name:s?,format:s?,mode:s?",
         .mhandler.cmd_new = qmp_marshal_input_blockdev_snapshot_sync,
     },
 
@@ -1134,7 +1141,9 @@ snapshot image, default is qcow2.
 Arguments:
 
 - "device": device name to snapshot (json-string)
+- "node-name": graph node name to snapshot (json-string)
 - "snapshot-file": name of new image file (json-string)
+- "snapshot-node-name": graph node name of the new snapshot (json-string)
 - "mode": whether and how QEMU should create the snapshot file
   (NewImageMode, optional, default "absolute-paths")
 - "format": format of new image (json-string, optional)