@@ -15,15 +15,6 @@ func init() {

 // Placeholder interfaces, to be replaced

 // at integration.

-type Image interface {

-	ID() string

-	Parent() (Image, error)

-	Path() string

-}

-

-type Change interface {

-}

-

 // End of placeholder interfaces.

 type Driver struct {

@@ -46,54 +37,45 @@ func (d *Driver) Cleanup() error {

 	return d.DeviceSet.Shutdown()

 }

-func (d *Driver) OnCreate(img Image, layer archive.Archive) error {

-	// Determine the source of the snapshot (parent id or init device)

-	var parentID string

-	if parent, err := img.Parent(); err != nil {

-		return err

-	} else if parent != nil {

-		parentID = parent.ID()

-	}

-	// Create the device for this image by snapshotting source

-	if err := d.DeviceSet.AddDevice(img.ID(), parentID); err != nil {

-		return err

-	}

-	// Mount the device in rootfs

-	mp := d.mountpoint(img.ID())

-	if err := os.MkdirAll(mp, 0700); err != nil {

-		return err

-	}

-	if err := d.DeviceSet.MountDevice(img.ID(), mp, false); err != nil {

-		return err

-	}

-	// Apply the layer as a diff

-	if layer != nil {

-		if err := archive.ApplyLayer(mp, layer); err != nil {

-			return err

-		}

-	}

-	return nil

+func (d *Driver) Create(id string, parent string) error {

+	return d.DeviceSet.AddDevice(id, parent)

 }

-func (d *Driver) OnRemove(img Image) error {

-	id := img.ID()

-	if err := d.DeviceSet.RemoveDevice(id); err != nil {

-		return fmt.Errorf("Unable to remove device for %v: %v", id, err)

-	}

-	return nil

+func (d *Driver) Remove(id string) error {

+	return d.DeviceSet.RemoveDevice(id)

 }

-func (d *Driver) mountpoint(id string) string {

-	if d.home == "" {

-		return ""

+func (d *Driver) Get(id string) (string, error) {

+	mp := path.Join(d.home, "mnt", id)

+	if err := d.mount(id, mp); err != nil {

+		return "", err

 	}

-	return path.Join(d.home, "mnt", id)

+	return mp, nil

 }

-func (d *Driver) Changes(img *Image, dest string) ([]Change, error) {

+func (d *Driver) Diff(id string) (archive.Archive, error) {

 	return nil, fmt.Errorf("Not implemented")

 }

-func (d *Driver) Layer(img *Image, dest string) (archive.Archive, error) {

+func (d *Driver) DiffSize(id string) (int64, error) {

+	return -1, fmt.Errorf("Not implemented")

+}

+

+func (d *Driver) Changes(id string) ([]graphdriver.Change, error) {

 	return nil, fmt.Errorf("Not implemented")

 }

+

+func (d *Driver) mount(id, mp string) error {

+	// Create the target directories if they don't exist

+	if err := os.MkdirAll(mp, 0755); err != nil && !os.IsExist(err) {

+		return err

+	}

+	// If mountpoint is already mounted, do nothing

+	if mounted, err := Mounted(mp); err != nil {

+		return fmt.Errorf("Error checking mountpoint: %s", err)

+	} else if mounted {

+		return nil

+	}

+	// Mount the device

+	return d.DeviceSet.MountDevice(id, mp, false)

+}

@@ -6,32 +6,6 @@ import (

 	"testing"

 )

-type TestImage struct {

-	id	string

-	path	string

-}

-

-func (img *TestImage) ID() string {

-	return img.id

-}

-

-func (img *TestImage) Path() string {

-	return img.path

-}

-

-func (img *TestImage) Parent() (Image, error) {

-	return nil, nil

-}

-

-

-

-func mkTestImage(t *testing.T) Image {

-	return &TestImage{

-		path:	mkTestDirectory(t),

-		id:	"4242",

-	}

-}

-

 func mkTestDirectory(t *testing.T) string {

 	dir, err := ioutil.TempDir("", "docker-test-devmapper-")

 	if err != nil {

@@ -43,19 +17,27 @@ func mkTestDirectory(t *testing.T) string {

 func TestInit(t *testing.T) {

 	home := mkTestDirectory(t)

 	defer os.RemoveAll(home)

-	plugin, err := Init(home)

+	driver, err := Init(home)

 	if err != nil {

 		t.Fatal(err)

 	}

 	defer func() {

 		return

-		if err := plugin.Cleanup(); err != nil {

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

 			t.Fatal(err)

 		}

 	}()

-	img := mkTestImage(t)

-	defer os.RemoveAll(img.(*TestImage).path)

-	if err := plugin.OnCreate(img, nil); err != nil {

+	id := "foo"

+	if err := driver.Create(id, ""); err != nil {

+		t.Fatal(err)

+	}

+	dir, err := driver.Get(id)

+	if err != nil {

+		t.Fatal(err)

+	}

+	if st, err := os.Stat(dir); err != nil {

 		t.Fatal(err)

+	} else if !st.IsDir() {

+		t.Fatalf("Get(%V) did not return a directory", id)

 	}

 }

new file mode 100644

@@ -0,0 +1,27 @@

+package devmapper

+

+import (

+	"os"

+	"path/filepath"

+	"syscall"

+)

+

+// FIXME: this is copy-pasted from the aufs driver.

+// It should be moved into the core.

+

+func Mounted(mountpoint string) (bool, error) {

+	mntpoint, err := os.Stat(mountpoint)

+	if err != nil {

+		if os.IsNotExist(err) {

+			return false, nil

+		}

+		return false, err

+	}

+	parent, err := os.Stat(filepath.Join(mountpoint, ".."))

+	if err != nil {

+		return false, err

+	}

+	mntpointSt := mntpoint.Sys().(*syscall.Stat_t)

+	parentSt := parent.Sys().(*syscall.Stat_t)

+	return mntpointSt.Dev != parentSt.Dev, nil

+}

@@ -8,6 +8,7 @@ import (

 	"github.com/dotcloud/docker/gograph"

 	"github.com/dotcloud/docker/utils"

 	"github.com/dotcloud/docker/graphdriver"

+	_ "github.com/dotcloud/docker/devmapper"

 	"io"

 	"io/ioutil"

 	"log"