hashedPayload := req.Header.Get("x-amz-content-sha256")
	if hashedPayload == "" {
		return "", fmt.Errorf("Invalid hashed payload")
	}

	// Set x-amz-date.
	req.Header.Set("x-amz-date", currTime.Format(iso8601Format))

	// Get header map.
	headerMap := make(map[string][]string)
	for k, vv := range req.Header {
		// If request header key is not in ignored headers, then add it.

	tags["merrs"] = joinErrs(errs)
	tags["derrs"] = fmt.Sprintf("%v", dataErrsByPart)
	if m.IsValid() {
		tags["sz"] = strconv.FormatInt(m.Size, 10)
		tags["mt"] = m.ModTime.Format(iso8601Format)
		tags["d:p"] = fmt.Sprintf("%d:%d", m.Erasure.DataBlocks, m.Erasure.ParityBlocks)
	} else {
		tags["invalid"] = "1"
		tags["d:p"] = fmt.Sprintf("%d:%d", er.setDriveCount-er.defaultParityCount, er.defaultParityCount)