devmapper: port to the new driver API and reactivate driver

devmapper/driver.go

@@ -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)
+}

devmapper/driver_test.go

@@ -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)
 	}
 }

devmapper/mount.go

@@ -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
+}

runtime.go

@@ -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"