@@ -400,21 +400,20 @@ func (container *Container) AddMountPointWithVolume(destination string, vol volu

 func (container *Container) UnmountVolumes(volumeEventLog func(name, action string, attributes map[string]string)) error {

 	var errors []string

 	for _, volumeMount := range container.MountPoints {

-		// Check if the mountpoint has an ID, this is currently the best way to tell if it's actually mounted

-		// TODO(cpuguyh83): there should be a better way to handle this

-		if volumeMount.Volume != nil && volumeMount.ID != "" {

-			if err := volumeMount.Volume.Unmount(volumeMount.ID); err != nil {

-				errors = append(errors, err.Error())

-				continue

-			}

-			volumeMount.ID = ""

+		if volumeMount.Volume == nil {

+			continue

+		}

-			attributes := map[string]string{

-				"driver":    volumeMount.Volume.DriverName(),

-				"container": container.ID,

-			}

-			volumeEventLog(volumeMount.Volume.Name(), "unmount", attributes)

+		if err := volumeMount.Cleanup(); err != nil {

+			errors = append(errors, err.Error())

+			continue

+		}

+

+		attributes := map[string]string{

+			"driver":    volumeMount.Volume.DriverName(),

+			"container": container.ID,

 		}

+		volumeEventLog(volumeMount.Volume.Name(), "unmount", attributes)

 	}

 	if len(errors) > 0 {

 		return fmt.Errorf("error while unmounting volumes for container %s: %s", container.ID, strings.Join(errors, "; "))

@@ -616,3 +616,18 @@ func (s *DockerExternalVolumeSuite) TestExternalVolumeDriverUnmountOnMountFail(c

 	out, _ = s.d.Cmd("run", "-w", "/foo", "-v", "testumount:/foo", "busybox", "true")

 	c.Assert(s.ec.unmounts, checker.Equals, 0, check.Commentf(out))

 }

+

+func (s *DockerExternalVolumeSuite) TestExternalVolumeDriverUnmountOnCp(c *check.C) {

+	s.d.StartWithBusybox(c)

+	s.d.Cmd("volume", "create", "-d", "test-external-volume-driver", "--name=test")

+

+	out, _ := s.d.Cmd("run", "-d", "--name=test", "-v", "test:/foo", "busybox", "/bin/sh", "-c", "touch /test && top")

+	c.Assert(s.ec.mounts, checker.Equals, 1, check.Commentf(out))

+

+	out, _ = s.d.Cmd("cp", "test:/test", "/tmp/test")

+	c.Assert(s.ec.mounts, checker.Equals, 2, check.Commentf(out))

+	c.Assert(s.ec.unmounts, checker.Equals, 1, check.Commentf(out))

+

+	out, _ = s.d.Cmd("kill", "test")

+	c.Assert(s.ec.unmounts, checker.Equals, 2, check.Commentf(out))

+}

@@ -120,6 +120,28 @@ type MountPoint struct {

 	// Sepc is a copy of the API request that created this mount.

 	Spec mounttypes.Mount

+

+	// Track usage of this mountpoint

+	// Specicially needed for containers which are running and calls to `docker cp`

+	// because both these actions require mounting the volumes.

+	active int

+}

+

+// Cleanup frees resources used by the mountpoint

+func (m *MountPoint) Cleanup() error {

+	if m.Volume == nil || m.ID == "" {

+		return nil

+	}

+

+	if err := m.Volume.Unmount(m.ID); err != nil {

+		return errors.Wrapf(err, "error unmounting volume %s", m.Volume.Name())

+	}

+

+	m.active--

+	if m.active == 0 {

+		m.ID = ""

+	}

+	return nil

 }

 // Setup sets up a mount point by either mounting the volume if it is

@@ -147,12 +169,16 @@ func (m *MountPoint) Setup(mountLabel string, rootUID, rootGID int) (path string

 		if err != nil {

 			return "", errors.Wrapf(err, "error while mounting volume '%s'", m.Source)

 		}

+

 		m.ID = id

+		m.active++

 		return path, nil

 	}

+

 	if len(m.Source) == 0 {

 		return "", fmt.Errorf("Unable to setup mount point, neither source nor volume defined")

 	}

+

 	// system.MkdirAll() produces an error if m.Source exists and is a file (not a directory),

 	if m.Type == mounttypes.TypeBind {

 		// idtools.MkdirAllNewAs() produces an error if m.Source exists and is a file (not a directory)