diff --git a/pkg/ioutil/pagewriter.go b/pkg/ioutil/pagewriter.go
index 72de1593d..cf9a8dc66 100644
--- a/pkg/ioutil/pagewriter.go
+++ b/pkg/ioutil/pagewriter.go
@@ -95,12 +95,23 @@ func (pw *PageWriter) Write(p []byte) (n int, err error) {
 	return n, werr
 }
 
+// Flush flushes buffered data.
 func (pw *PageWriter) Flush() error {
-	if pw.bufferedBytes == 0 {
-		return nil
-	}
-	_, err := pw.w.Write(pw.buf[:pw.bufferedBytes])
-	pw.pageOffset = (pw.pageOffset + pw.bufferedBytes) % pw.pageBytes
-	pw.bufferedBytes = 0
+	_, err := pw.flush()
 	return err
 }
+
+// FlushN flushes buffered data and returns the number of written bytes.
+func (pw *PageWriter) FlushN() (int, error) {
+	return pw.flush()
+}
+
+func (pw *PageWriter) flush() (int, error) {
+	if pw.bufferedBytes == 0 {
+		return 0, nil
+	}
+	n, err := pw.w.Write(pw.buf[:pw.bufferedBytes])
+	pw.pageOffset = (pw.pageOffset + pw.bufferedBytes) % pw.pageBytes
+	pw.bufferedBytes = 0
+	return n, err
+}