Fix GPFS collector last state handling

collectors/gpfsMetric.go

@@ -70,6 +70,7 @@ func (m *GpfsCollector) Init(config json.RawMessage) error {
 	for _, fs := range m.config.ExcludeFilesystem {
 		m.skipFS[fs] = struct{}{}
 	}
+	m.lastState = make(map[string]GpfsCollectorLastState)
 
 	// GPFS / IBM Spectrum Scale file system statistics can only be queried by user root
 	user, err := user.Current()
@@ -162,13 +163,18 @@ func (m *GpfsCollector) Read(interval time.Duration, output chan lp.CCMetric) {
 			continue
 		}
 
+		// Add filesystem tag
 		m.tags["filesystem"] = filesystem
+
+		// Create initial last state
+		if m.config.SendBandwidths {
 			if _, ok := m.lastState[filesystem]; !ok {
 				m.lastState[filesystem] = GpfsCollectorLastState{
 					bytesRead:    -1,
 					bytesWritten: -1,
 				}
 			}
+		}
 
 		// return code
 		rc, err := strconv.Atoi(key_value["_rc_"])