v4.19.13 snapshot.
diff --git a/fs/btrfs/math.h b/fs/btrfs/math.h
new file mode 100644
index 0000000..75246f2
--- /dev/null
+++ b/fs/btrfs/math.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2012 Fujitsu. All rights reserved.
+ * Written by Miao Xie <miaox@cn.fujitsu.com>
+ */
+
+#ifndef BTRFS_MATH_H
+#define BTRFS_MATH_H
+
+#include <asm/div64.h>
+
+static inline u64 div_factor(u64 num, int factor)
+{
+ if (factor == 10)
+ return num;
+ num *= factor;
+ return div_u64(num, 10);
+}
+
+static inline u64 div_factor_fine(u64 num, int factor)
+{
+ if (factor == 100)
+ return num;
+ num *= factor;
+ return div_u64(num, 100);
+}
+
+#endif