Merge pull request #10220 from ping40/pagewriter

pkg/ioutil: n is equal or greater than cw.writeBytes

pkg/ioutil/pagewriter_test.go

@@ -37,8 +37,8 @@ func TestPageWriterRandom(t *testing.T) {
 	if cw.writeBytes > n {
 		t.Fatalf("wrote %d bytes to io.Writer, but only wrote %d bytes", cw.writeBytes, n)
 	}
-	if cw.writeBytes-n > pageBytes {
-		t.Fatalf("got %d bytes pending, expected less than %d bytes", cw.writeBytes-n, pageBytes)
+	if n-cw.writeBytes > pageBytes {
+		t.Fatalf("got %d bytes pending, expected less than %d bytes", n-cw.writeBytes, pageBytes)
 	}
 	t.Logf("total writes: %d", cw.writes)
 	t.Logf("total write bytes: %d (of %d)", cw.writeBytes, n)