devmapper: add and use removeDeviceAndWait helper

This adds a function that calls the lowlevel removeDevice
and then waits for it to finish.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

graphdriver/devmapper/deviceset.go

@@ -632,28 +632,33 @@ func (devices *DeviceSet) deactivateDevice(hash string) error {
 		return err
 	}
 	if devinfo.Exists != 0 {
-		if err := removeDevice(devname); err != nil {
+		if err := devices.removeDeviceAndWait(devname); err != nil {
 			utils.Debugf("\n--->Err: %s\n", err)
 			return err
 		}
-		if err := devices.waitRemove(hash); err != nil {
-			return err
-		}
 	}
 
 	return nil
 }
 
+// Issues the underlying dm remove operation and then waits
+// for it to finish.
+func (devices *DeviceSet) removeDeviceAndWait(devname string) error {
+	if err := removeDevice(devname); err != nil {
+		return err
+	}
+	if err := devices.waitRemove(devname); err != nil {
+		return err
+	}
+	return nil
+}
+
 // waitRemove blocks until either:
 // a) the device registered at <device_set_prefix>-<hash> is removed,
 // or b) the 1 second timeout expires.
-func (devices *DeviceSet) waitRemove(hash string) error {
-	utils.Debugf("[deviceset %s] waitRemove(%s)", devices.devicePrefix, hash)
-	defer utils.Debugf("[deviceset %s] waitRemove(%) END", devices.devicePrefix, hash)
-	devname, err := devices.byHash(hash)
-	if err != nil {
-		return err
-	}
+func (devices *DeviceSet) waitRemove(devname string) error {
+	utils.Debugf("[deviceset %s] waitRemove(%s)", devices.devicePrefix, devname)
+	defer utils.Debugf("[deviceset %s] waitRemove(%s) END", devices.devicePrefix, devname)
 	i := 0
 	for ; i < 1000; i += 1 {
 		devinfo, err := getInfo(devname)