db/update/VirtualDirectory: add LockMakeVirtualDirectoryIfModified()

src/db/update/VirtualDirectory.cxx

@@ -18,6 +18,7 @@
  */
 
 #include "Walk.hxx"
+#include "db/DatabaseLock.hxx"
 #include "db/plugins/simple/Directory.hxx"
 #include "storage/FileInfo.hxx"
 
@@ -49,3 +50,14 @@ UpdateWalk::MakeVirtualDirectoryIfModified(Directory &parent, const char *name,
 	directory->device = virtual_device;
 	return directory;
 }
+
+Directory *
+UpdateWalk::LockMakeVirtualDirectoryIfModified(Directory &parent,
+					       const char *name,
+					       const StorageFileInfo &info,
+					       unsigned virtual_device) noexcept
+{
+	const ScopeDatabaseLock protect;
+	return MakeVirtualDirectoryIfModified(parent, name,
+					      info, virtual_device);
+}

src/db/update/Walk.hxx

@@ -150,6 +150,11 @@ private:
 						  const StorageFileInfo &info,
 						  unsigned virtual_device) noexcept;
 
+	Directory *LockMakeVirtualDirectoryIfModified(Directory &parent,
+						      const char *name,
+						      const StorageFileInfo &info,
+						      unsigned virtual_device) noexcept;
+
 	Directory *DirectoryMakeChildChecked(Directory &parent,
 					     const char *uri_utf8,
 					     const char *name_utf8) noexcept;