qemu: block: Add helper for generating snapshot transaction for -blockdev

For the modern use cases we are going to use 'blockdev-snapshot' instead
of 'blockdev-snapshot-sync'.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_block.c

@@ -1886,6 +1886,21 @@ qemuBlockSnapshotAddLegacy(virJSONValuePtr actions,
 }
 
 
+int
+qemuBlockSnapshotAddBlockdev(virJSONValuePtr actions,
+                             virDomainDiskDefPtr disk,
+                             virStorageSourcePtr newsrc)
+{
+    if (qemuMonitorJSONTransactionAdd(actions, "blockdev-snapshot",
+                                      "s:node", disk->src->nodeformat,
+                                      "s:overlay", newsrc->nodeformat,
+                                      NULL) < 0)
+        return -1;
+
+    return 0;
+}
+
+
 /**
  * qemuBlockStorageGetCopyOnReadProps:
  * @disk: disk with copy-on-read enabled

src/qemu/qemu_block.h

@@ -163,6 +163,11 @@ qemuBlockSnapshotAddLegacy(virJSONValuePtr actions,
                            virStorageSourcePtr newsrc,
                            bool reuse);
 
+int
+qemuBlockSnapshotAddBlockdev(virJSONValuePtr actions,
+                             virDomainDiskDefPtr disk,
+                             virStorageSourcePtr newsrc);
+
 int
 qemuBlockStorageSourceCreateGetFormatProps(virStorageSourcePtr src,
                                            virStorageSourcePtr backing,