Exportar Gridview a excel a travez de un reportviewer

 Protected Sub btn_Exportar_Click(sender As Object, e As EventArgs) Handles btn_Exportar.Click
        Dim warnings As Warning()
        Dim streamids As String()
        Dim mimeType As String
        Dim encoding As String
        Dim extension As String
        Dim filename As String
        'Consulta que devuelve el dataset con los datos en pantalla
        Dim ds As DataSet = clsusr.ExportarUsr(GrillaUsuario, txtUsr_log.Text.Trim(), txtNit_Usr.Text.Trim(), txtNom_Ape.Text.Trim(), txtNit_Emp.Text.Trim(), txtRac_soc.Text.Trim())
        Dim ds2 As New DataTable
        'le asigno la tabla 0 del dataset al datatable
        ds2 = ds.Tables(0)

        'le asigno la fuente al reporte
        Dim datos As New ReportDataSource("DataSet1", ds2)
        'le indico donde esta la ruta del reporte a exportar
        ReportViewer1.LocalReport.ReportPath = ("Reportes\ReporteMantencionUsrIe.rdlc")
        reportViewer1.ProcessingMode = ProcessingMode.Local
        ReportViewer1.LocalReport.DataSources.Clear()
        'le agrego el datataset al reporte
        reportViewer1.LocalReport.DataSources.Add(New ReportDataSource("DataSet1", ds.Tables(0)))
        reportViewer1.LocalReport.Refresh()

        'creo un byte con la extension deseada
        Dim bytes As Byte() = ReportViewer1.LocalReport.Render("EXCELOPENXML", Nothing, mimeType, Encoding, extension, streamids, warnings)
        'filename = String.Format("{0}.{1}", "BitacoraWeb_usuario_" & txtusr.Text & "_" & txtdesde.Text.Replace("/", "-") & "_" & txtHasta.Text.Replace("/", "-"), "xlsx")
        'le asigno un nombre al archivo
        filename = String.Format("Busqueda_Usuarios_Empresa", "xlsx")

        Response.ClearHeaders()
        Response.Clear()
        Response.AddHeader("Content-Disposition", Convert.ToString("attachment;filename=") & filename)
        Response.ContentType = mimeType
        Response.BinaryWrite(bytes)
        Response.Flush()
        Response.[End]()
    End Sub