Update overlay snapshot driver to use metastore

Update tests to use boltdb.
Update test suite to pass context.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

snapshot/btrfs/btrfs_test.go

@@ -21,7 +21,7 @@ const (
 
 func TestBtrfs(t *testing.T) {
 	testutil.RequiresRoot(t)
-	testsuite.SnapshotterSuite(t, "Btrfs", func(root string) (snapshot.Snapshotter, func(), error) {
+	testsuite.SnapshotterSuite(t, "Btrfs", func(ctx context.Context, root string) (snapshot.Snapshotter, func(), error) {
 		device := setupBtrfsLoopbackDevice(t, root)
 		snapshotter, err := NewSnapshotter(device.deviceName, root)
 		if err != nil {

snapshot/overlay/overlay.go

@@ -7,12 +7,13 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"sync"
 
 	"github.com/docker/containerd"
+	"github.com/docker/containerd/log"
 	"github.com/docker/containerd/plugin"
 	"github.com/docker/containerd/snapshot"
-	digest "github.com/opencontainers/go-digest"
+	"github.com/docker/containerd/snapshot/storage"
+	"github.com/docker/containerd/snapshot/storage/boltdb"
 	"github.com/pkg/errors"
 )
 
@@ -20,32 +21,40 @@ func init() {
 	plugin.Register("snapshot-overlay", &plugin.Registration{
 		Type: plugin.SnapshotPlugin,
 		Init: func(ic *plugin.InitContext) (interface{}, error) {
-			return NewSnapshotter(filepath.Join(ic.Root, "snapshot", "overlay"))
+			root := filepath.Join(ic.Root, "snapshot", "overlay")
+			ms, err := boltdb.NewMetaStore(ic.Context, filepath.Join(root, "metadata.db"))
+			if err != nil {
+				return nil, err
+			}
+			return NewSnapshotter(root, ms)
 		},
 	})
 }
 
 type Snapshotter struct {
 	root string
-	links *cache
+	ms   storage.MetaStore
 }
 
-func NewSnapshotter(root string) (snapshot.Snapshotter, error) {
+type activeSnapshot struct {
+	id       string
+	name     string
+	parentID interface{}
+	readonly bool
+}
+
+func NewSnapshotter(root string, ms storage.MetaStore) (snapshot.Snapshotter, error) {
 	if err := os.MkdirAll(root, 0700); err != nil {
 		return nil, err
 	}
-	for _, p := range []string{
+
-		"committed", // committed snapshots
+	if err := os.MkdirAll(filepath.Join(root, "snapshots"), 0700); err != nil {
-		"active",    // active snapshots
-		"index",     // snapshots by hashed name
-	} {
-		if err := os.MkdirAll(filepath.Join(root, p), 0700); err != nil {
 		return nil, err
 	}
-	}
+
 	return &Snapshotter{
 		root: root,
-		links: newCache(),
+		ms:   ms,
 	}, nil
 }
 
@@ -55,86 +64,20 @@ func NewSnapshotter(root string) (snapshot.Snapshotter, error) {
 // Should be used for parent resolution, existence checks and to discern
 // the kind of snapshot.
 func (o *Snapshotter) Stat(ctx context.Context, key string) (snapshot.Info, error) {
-	path, err := o.links.get(filepath.Join(o.root, "index", hash(key)))
+	ctx, t, err := o.ms.TransactionContext(ctx, false)
-	if err != nil {
-		if !os.IsNotExist(err) {
-			return snapshot.Info{}, err
-		}
-
-		return snapshot.Info{}, errors.Errorf("snapshot %v not found", key)
-	}
-
-	// TODO(stevvooe): We don't confirm the name to avoid the lookup cost.
-	return o.stat(path)
-}
-
-func (o *Snapshotter) stat(path string) (snapshot.Info, error) {
-	ppath, err := o.links.get(filepath.Join(path, "parent"))
-	if err != nil {
-		if !os.IsNotExist(err) {
-			return snapshot.Info{}, err
-		}
-
-		// no parent
-	}
-
-	kp, err := ioutil.ReadFile(filepath.Join(path, "name"))
 	if err != nil {
 		return snapshot.Info{}, err
 	}
-
+	defer t.Rollback()
-	var parent string
+	return o.ms.Stat(ctx, key)
-	if ppath != "" {
-		p, err := ioutil.ReadFile(filepath.Join(ppath, "name"))
-		if err != nil {
-			return snapshot.Info{}, err
-		}
-		parent = string(p)
-	}
-
-	ro := true
-	kind := snapshot.KindCommitted
-	if strings.HasPrefix(path, filepath.Join(o.root, "active")) {
-		// TODO(stevvooe): Maybe there is a better way?
-		kind = snapshot.KindActive
-
-		// TODO(stevvooe): We haven't introduced this to overlay yet.
-		// We'll add it when we add tests for it.
-		ro = false
-	}
-
-	return snapshot.Info{
-		Name:     string(kp),
-		Parent:   parent,
-		Kind:     kind,
-		Readonly: ro,
-	}, nil
 }
 
 func (o *Snapshotter) Prepare(ctx context.Context, key, parent string) ([]containerd.Mount, error) {
-	active, err := o.newActiveDir(key, false)
+	return o.createActive(ctx, key, parent, false)
-	if err != nil {
-		return nil, err
-	}
-	if parent != "" {
-		if err := active.setParent(parent); err != nil {
-			return nil, err
-		}
-	}
-	return active.mounts(o.links)
 }
 
 func (o *Snapshotter) View(ctx context.Context, key, parent string) ([]containerd.Mount, error) {
-	active, err := o.newActiveDir(key, true)
+	return o.createActive(ctx, key, parent, true)
-	if err != nil {
-		return nil, err
-	}
-	if parent != "" {
-		if err := active.setParent(parent); err != nil {
-			return nil, err
-		}
-	}
-	return active.mounts(o.links)
 }
 
 // Mounts returns the mounts for the transaction identified by key. Can be
@@ -142,263 +85,208 @@ func (o *Snapshotter) View(ctx context.Context, key, parent string) ([]container
 //
 // This can be used to recover mounts after calling View or Prepare.
 func (o *Snapshotter) Mounts(ctx context.Context, key string) ([]containerd.Mount, error) {
-	active := o.getActive(key)
+	ctx, t, err := o.ms.TransactionContext(ctx, false)
-	return active.mounts(o.links)
+	if err != nil {
+		return nil, err
+	}
+	active, err := o.ms.GetActive(ctx, key)
+	t.Rollback()
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to get active mount")
+	}
+	return o.mounts(active), nil
 }
 
 func (o *Snapshotter) Commit(ctx context.Context, name, key string) error {
-	active := o.getActive(key)
+	ctx, t, err := o.ms.TransactionContext(ctx, true)
-	return active.commit(name, o.links)
+	if err != nil {
+		return err
+	}
+	if _, err := o.ms.Commit(ctx, key, name); err != nil {
+		if rerr := t.Rollback(); rerr != nil {
+			log.G(ctx).WithError(rerr).Warn("Failure rolling back transaction")
+		}
+		return errors.Wrap(err, "failed to commit snapshot")
+	}
+	return t.Commit()
 }
 
 // Remove abandons the transaction identified by key. All resources
 // associated with the key will be removed.
-func (o *Snapshotter) Remove(ctx context.Context, key string) error {
+func (o *Snapshotter) Remove(ctx context.Context, key string) (err error) {
-	panic("not implemented")
+	ctx, t, err := o.ms.TransactionContext(ctx, true)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		if err != nil && t != nil {
+			if rerr := t.Rollback(); rerr != nil {
+				log.G(ctx).WithError(rerr).Warn("Failure rolling back transaction")
+			}
+		}
+	}()
+
+	id, err := o.ms.Remove(ctx, key)
+	if err != nil {
+		return errors.Wrap(err, "failed to remove")
+	}
+
+	path := filepath.Join(o.root, "snapshots", id)
+	renamed := filepath.Join(o.root, "snapshots", "rm-"+id)
+	if err := os.Rename(path, renamed); err != nil {
+		return errors.Wrap(err, "failed to rename")
+	}
+
+	err = t.Commit()
+	t = nil
+	if err != nil {
+		if err1 := os.Rename(renamed, path); err1 != nil {
+			// May cause inconsistent data on disk
+			log.G(ctx).WithError(err1).WithField("path", renamed).Errorf("Failed to rename after failed commit")
+		}
+		return errors.Wrap(err, "failed to commit")
+	}
+	if err := os.RemoveAll(renamed); err != nil {
+		// Must be cleaned up, any "rm-*" could be removed if no active transactions
+		log.G(ctx).WithError(err).WithField("path", renamed).Warnf("Failed to remove root filesystem")
+	}
+
+	return nil
 }
 
 // Walk the committed snapshots.
 func (o *Snapshotter) Walk(ctx context.Context, fn func(context.Context, snapshot.Info) error) error {
-	root := filepath.Join(o.root, "index")
+	ctx, t, err := o.ms.TransactionContext(ctx, false)
-	return filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
 	if err != nil {
 		return err
 	}
-
+	defer t.Rollback()
-		if path == root {
+	return o.ms.Walk(ctx, fn)
-			return nil
-		}
-
-		if fi.Mode()&os.ModeSymlink == 0 {
-			// only follow links
-			return filepath.SkipDir
-		}
-
-		target, err := o.links.get(path)
-		if err != nil {
-			if !os.IsNotExist(err) {
-				return err
-			}
-		}
-
-		si, err := o.stat(target)
-		if err != nil {
-			return err
-		}
-
-		if err := fn(ctx, si); err != nil {
-			return err
-		}
-
-		return nil
-	})
 }
 
-func (o *Snapshotter) newActiveDir(key string, readonly bool) (*activeDir, error) {
+func (o *Snapshotter) createActive(ctx context.Context, key, parent string, readonly bool) ([]containerd.Mount, error) {
 	var (
-		path      = filepath.Join(o.root, "active", hash(key))
+		path        string
-		name      = filepath.Join(path, "name")
+		snapshotDir = filepath.Join(o.root, "snapshots")
-		indexlink = filepath.Join(o.root, "index", hash(key))
 	)
-	a := &activeDir{
+
-		path:         path,
+	td, err := ioutil.TempDir(snapshotDir, "new-")
-		committedDir: filepath.Join(o.root, "committed"),
+	if err != nil {
-		indexlink:    indexlink,
+		return nil, errors.Wrap(err, "failed to create temp dir")
+	}
+	defer func() {
+		if err != nil {
+			if td != "" {
+				if err1 := os.RemoveAll(td); err1 != nil {
+					err = errors.Wrapf(err, "remove failed: %v", err1)
+				}
+			}
+			if path != "" {
+				if err1 := os.RemoveAll(path); err1 != nil {
+					err = errors.Wrapf(err, "failed to remove path: %v", err1)
+				}
+			}
+		}
+	}()
+
+	if err = os.MkdirAll(filepath.Join(td, "fs"), 0700); err != nil {
+		return nil, err
 	}
 	if !readonly {
-		for _, p := range []string{
+		if err = os.MkdirAll(filepath.Join(td, "work"), 0700); err != nil {
-			"work",
-			"fs",
-		} {
-			if err := os.MkdirAll(filepath.Join(path, p), 0700); err != nil {
-				a.delete()
-				return nil, err
-			}
-		}
-	} else {
-		if err := os.MkdirAll(filepath.Join(path, "fs"), 0700); err != nil {
-			a.delete()
 			return nil, err
 		}
 	}
 
-	if err := ioutil.WriteFile(name, []byte(key), 0644); err != nil {
+	ctx, t, err := o.ms.TransactionContext(ctx, true)
-		a.delete()
+	if err != nil {
 		return nil, err
 	}
 
-	// link from namespace
+	active, err := o.ms.CreateActive(ctx, key, parent, readonly)
-	if err := os.Symlink(path, indexlink); err != nil {
+	if err != nil {
-		a.delete()
+		if rerr := t.Rollback(); rerr != nil {
-		return nil, err
+			// TODO: log rollback error
+		}
+		return nil, errors.Wrap(err, "failed to create active")
 	}
 
-	return a, nil
+	path = filepath.Join(snapshotDir, active.ID)
+	if err := os.Rename(td, path); err != nil {
+		if rerr := t.Rollback(); rerr != nil {
+			// TODO: log rollback error
+		}
+		return nil, errors.Wrap(err, "failed to rename")
+	}
+	td = ""
+
+	if err := t.Commit(); err != nil {
+		return nil, errors.Wrap(err, "commit failed")
+	}
+
+	return o.mounts(active), nil
 }
 
-func (o *Snapshotter) getActive(key string) *activeDir {
+func (o *Snapshotter) mounts(active storage.Active) []containerd.Mount {
-	return &activeDir{
+	if len(active.ParentIDs) == 0 {
-		path:         filepath.Join(o.root, "active", hash(key)),
-		committedDir: filepath.Join(o.root, "committed"),
-		indexlink:    filepath.Join(o.root, "index", hash(key)),
-	}
-}
-
-func hash(k string) string {
-	return digest.FromString(k).Hex()
-}
-
-type activeDir struct {
-	committedDir string
-	path         string
-	indexlink    string
-}
-
-func (a *activeDir) delete() error {
-	return os.RemoveAll(a.path)
-}
-
-func (a *activeDir) setParent(name string) error {
-	return os.Symlink(filepath.Join(a.committedDir, hash(name)), filepath.Join(a.path, "parent"))
-}
-
-func (a *activeDir) commit(name string, c *cache) error {
-	if _, err := os.Stat(filepath.Join(a.path, "fs")); err != nil {
-		if os.IsNotExist(err) {
-			return errors.New("cannot commit view")
-		}
-		return err
-	}
-
-	// TODO(stevvooe): This doesn't quite meet the current model. The new model
-	// is to copy all of this out and let the transaction continue. We don't
-	// really have tests for it yet, but this will be the spot to fix it.
-	//
-	// Nothing should be removed until remove is called on the active
-	// transaction.
-	if err := os.RemoveAll(filepath.Join(a.path, "work")); err != nil {
-		return err
-	}
-
-	if err := ioutil.WriteFile(filepath.Join(a.path, "name"), []byte(name), 0644); err != nil {
-		return err
-	}
-
-	c.invalidate(a.path) // clears parent cache, since we end up moving.
-	c.invalidate(filepath.Join(a.path, "parent"))
-	c.invalidate(a.indexlink)
-
-	committed := filepath.Join(a.committedDir, hash(name))
-	if err := os.Rename(a.path, committed); err != nil {
-		return err
-	}
-
-	if err := os.Remove(a.indexlink); err != nil {
-		return err
-	}
-
-	indexlink := filepath.Join(filepath.Dir(a.indexlink), hash(name))
-	return os.Symlink(committed, indexlink)
-}
-
-func (a *activeDir) mounts(c *cache) ([]containerd.Mount, error) {
-	var (
-		parents []string
-		err     error
-		current = a.path
-	)
-	for {
-		if current, err = c.get(filepath.Join(current, "parent")); err != nil {
-			if os.IsNotExist(err) {
-				break
-			}
-
-			return nil, err
-		}
-		parents = append(parents, filepath.Join(current, "fs"))
-	}
-	if len(parents) == 0 {
 		// if we only have one layer/no parents then just return a bind mount as overlay
 		// will not work
 		roFlag := "rw"
-		if _, err := os.Stat(filepath.Join(a.path, "work")); err != nil {
+		if active.Readonly {
-			if !os.IsNotExist(err) {
-				return nil, err
-			}
 			roFlag = "ro"
 		}
 
 		return []containerd.Mount{
 			{
-				Source: filepath.Join(a.path, "fs"),
+				Source: o.upperPath(active.ID),
 				Type:   "bind",
 				Options: []string{
 					roFlag,
 					"rbind",
 				},
 			},
-		}, nil
+		}
 	}
 	var options []string
 
-	if _, err := os.Stat(filepath.Join(a.path, "work")); err == nil {
+	if !active.Readonly {
 		options = append(options,
-			fmt.Sprintf("workdir=%s", filepath.Join(a.path, "work")),
+			fmt.Sprintf("workdir=%s", o.workPath(active.ID)),
-			fmt.Sprintf("upperdir=%s", filepath.Join(a.path, "fs")),
+			fmt.Sprintf("upperdir=%s", o.upperPath(active.ID)),
 		)
-	} else if !os.IsNotExist(err) {
+	} else if len(active.ParentIDs) == 1 {
-		return nil, err
-	} else if len(parents) == 1 {
 		return []containerd.Mount{
 			{
-				Source: parents[0],
+				Source: o.upperPath(active.ParentIDs[0]),
 				Type:   "bind",
 				Options: []string{
 					"ro",
 					"rbind",
 				},
 			},
-		}, nil
+		}
 	}
 
-	options = append(options, fmt.Sprintf("lowerdir=%s", strings.Join(parents, ":")))
+	parentPaths := make([]string, len(active.ParentIDs))
+	for i := range active.ParentIDs {
+		parentPaths[i] = o.upperPath(active.ParentIDs[i])
+	}
+
+	options = append(options, fmt.Sprintf("lowerdir=%s", strings.Join(parentPaths, ":")))
 	return []containerd.Mount{
 		{
 			Type:    "overlay",
 			Source:  "overlay",
 			Options: options,
 		},
-	}, nil
-}
-
-func newCache() *cache {
-	return &cache{
-		links: make(map[string]string),
 	}
+
 }
 
-type cache struct {
+func (o *Snapshotter) upperPath(id string) string {
-	mu    sync.Mutex
+	return filepath.Join(o.root, "snapshots", id, "fs")
-	links map[string]string
 }
 
-func (c *cache) get(path string) (string, error) {
+func (o *Snapshotter) workPath(id string) string {
-	c.mu.Lock()
+	return filepath.Join(o.root, "snapshots", id, "work")
-	defer c.mu.Unlock()
-	target, ok := c.links[path]
-	if !ok {
-		link, err := os.Readlink(path)
-		if err != nil {
-			return "", err
-		}
-		c.links[path], target = link, link
-	}
-	return target, nil
-}
-
-func (c *cache) invalidate(path string) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	delete(c.links, path)
 }

snapshot/overlay/overlay_test.go

@@ -11,20 +11,27 @@ import (
 
 	"github.com/docker/containerd"
 	"github.com/docker/containerd/snapshot"
+	"github.com/docker/containerd/snapshot/storage/boltdb"
 	"github.com/docker/containerd/snapshot/testsuite"
 	"github.com/docker/containerd/testutil"
 )
 
-func TestOverlay(t *testing.T) {
+func boltSnapshotter(ctx context.Context, root string) (snapshot.Snapshotter, func(), error) {
-	testutil.RequiresRoot(t)
+	store, err := boltdb.NewMetaStore(ctx, filepath.Join(root, "metadata.db"))
-	testsuite.SnapshotterSuite(t, "Overlay", func(root string) (snapshot.Snapshotter, func(), error) {
-		snapshotter, err := NewSnapshotter(root)
 	if err != nil {
-			t.Fatal(err)
+		return nil, nil, err
+	}
+	snapshotter, err := NewSnapshotter(root, store)
+	if err != nil {
+		return nil, nil, err
 	}
 
 	return snapshotter, func() {}, nil
-	})
+}
+
+func TestOverlay(t *testing.T) {
+	testutil.RequiresRoot(t)
+	testsuite.SnapshotterSuite(t, "Overlay", boltSnapshotter)
 }
 
 func TestOverlayMounts(t *testing.T) {
@@ -34,7 +41,7 @@ func TestOverlayMounts(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(root)
-	o, err := NewSnapshotter(root)
+	o, _, err := boltSnapshotter(ctx, root)
 	if err != nil {
 		t.Error(err)
 		return
@@ -51,7 +58,7 @@ func TestOverlayMounts(t *testing.T) {
 	if m.Type != "bind" {
 		t.Errorf("mount type should be bind but received %q", m.Type)
 	}
-	expected := filepath.Join(root, "active", hash("/tmp/test"), "fs")
+	expected := filepath.Join(root, "snapshots", "1", "fs")
 	if m.Source != expected {
 		t.Errorf("expected source %q but received %q", expected, m.Source)
 	}
@@ -70,7 +77,7 @@ func TestOverlayCommit(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(root)
-	o, err := NewSnapshotter(root)
+	o, _, err := boltSnapshotter(ctx, root)
 	if err != nil {
 		t.Error(err)
 		return
@@ -99,7 +106,7 @@ func TestOverlayOverlayMount(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(root)
-	o, err := NewSnapshotter(root)
+	o, _, err := boltSnapshotter(ctx, root)
 	if err != nil {
 		t.Error(err)
 		return
@@ -129,11 +136,10 @@ func TestOverlayOverlayMount(t *testing.T) {
 		t.Errorf("expected source %q but received %q", "overlay", m.Source)
 	}
 	var (
-		ah    = hash("/tmp/layer2")
+		bp    = getBasePath(ctx, o, root, "/tmp/layer2")
-		sh    = hash("base")
+		work  = "workdir=" + filepath.Join(bp, "work")
-		work  = "workdir=" + filepath.Join(root, "active", ah, "work")
+		upper = "upperdir=" + filepath.Join(bp, "fs")
-		upper = "upperdir=" + filepath.Join(root, "active", ah, "fs")
+		lower = "lowerdir=" + getParents(ctx, o, root, "/tmp/layer2")[0]
-		lower = "lowerdir=" + filepath.Join(root, "committed", sh, "fs")
 	)
 	for i, v := range []string{
 		work,
@@ -146,6 +152,40 @@ func TestOverlayOverlayMount(t *testing.T) {
 	}
 }
 
+func getBasePath(ctx context.Context, sn snapshot.Snapshotter, root, key string) string {
+	o := sn.(*Snapshotter)
+	ctx, t, err := o.ms.TransactionContext(ctx, false)
+	if err != nil {
+		panic(err)
+	}
+	defer t.Rollback()
+
+	active, err := o.ms.GetActive(ctx, key)
+	if err != nil {
+		panic(err)
+	}
+
+	return filepath.Join(root, "snapshots", active.ID)
+}
+
+func getParents(ctx context.Context, sn snapshot.Snapshotter, root, key string) []string {
+	o := sn.(*Snapshotter)
+	ctx, t, err := o.ms.TransactionContext(ctx, false)
+	if err != nil {
+		panic(err)
+	}
+	defer t.Rollback()
+	active, err := o.ms.GetActive(ctx, key)
+	if err != nil {
+		panic(err)
+	}
+	parents := make([]string, len(active.ParentIDs))
+	for i := range active.ParentIDs {
+		parents[i] = filepath.Join(root, "snapshots", active.ParentIDs[i], "fs")
+	}
+	return parents
+}
+
 func TestOverlayOverlayRead(t *testing.T) {
 	testutil.RequiresRoot(t)
 	ctx := context.TODO()
@@ -154,7 +194,7 @@ func TestOverlayOverlayRead(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(root)
-	o, err := NewSnapshotter(root)
+	o, _, err := boltSnapshotter(ctx, root)
 	if err != nil {
 		t.Error(err)
 		return
@@ -206,7 +246,7 @@ func TestOverlayView(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(root)
-	o, err := NewSnapshotter(root)
+	o, _, err := boltSnapshotter(ctx, root)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -228,7 +268,7 @@ func TestOverlayView(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if err := ioutil.WriteFile(filepath.Join(root, "active", hash(key), "fs", "foo"), []byte("hi, again"), 0660); err != nil {
+	if err := ioutil.WriteFile(filepath.Join(getParents(ctx, o, root, "/tmp/top")[0], "foo"), []byte("hi, again"), 0660); err != nil {
 		t.Fatal(err)
 	}
 	if err := o.Commit(ctx, "top", key); err != nil {
@@ -246,7 +286,7 @@ func TestOverlayView(t *testing.T) {
 	if m.Type != "bind" {
 		t.Errorf("mount type should be bind but received %q", m.Type)
 	}
-	expected := filepath.Join(root, "committed", hash("base"), "fs")
+	expected := getParents(ctx, o, root, "/tmp/view1")[0]
 	if m.Source != expected {
 		t.Errorf("expected source %q but received %q", expected, m.Source)
 	}
@@ -274,7 +314,8 @@ func TestOverlayView(t *testing.T) {
 	if len(m.Options) != 1 {
 		t.Errorf("expected 1 mount option but got %d", len(m.Options))
 	}
-	expected = fmt.Sprintf("lowerdir=%s:%s", filepath.Join(root, "committed", hash("top"), "fs"), filepath.Join(root, "committed", hash("base"), "fs"))
+	lowers := getParents(ctx, o, root, "/tmp/view2")
+	expected = fmt.Sprintf("lowerdir=%s:%s", lowers[0], lowers[1])
 	if m.Options[0] != expected {
 		t.Errorf("expected option %q but received %q", expected, m.Options[0])
 	}

snapshot/testsuite/testsuite.go

@@ -17,7 +17,7 @@ import (
 )
 
 // SnapshotterSuite runs a test suite on the snapshotter given a factory function.
-func SnapshotterSuite(t *testing.T, name string, snapshotterFn func(root string) (snapshot.Snapshotter, func(), error)) {
+func SnapshotterSuite(t *testing.T, name string, snapshotterFn func(ctx context.Context, root string) (snapshot.Snapshotter, func(), error)) {
 	t.Run("Basic", makeTest(t, name, snapshotterFn, checkSnapshotterBasic))
 	t.Run("StatActive", makeTest(t, name, snapshotterFn, checkSnapshotterStatActive))
 	t.Run("StatComitted", makeTest(t, name, snapshotterFn, checkSnapshotterStatCommitted))
@@ -25,8 +25,9 @@ func SnapshotterSuite(t *testing.T, name string, snapshotterFn func(root string)
 	t.Run("PreareViewFailingtest", makeTest(t, name, snapshotterFn, checkSnapshotterPrepareView))
 }
 
-func makeTest(t *testing.T, name string, snapshotterFn func(root string) (snapshot.Snapshotter, func(), error), fn func(t *testing.T, snapshotter snapshot.Snapshotter, work string)) func(t *testing.T) {
+func makeTest(t *testing.T, name string, snapshotterFn func(ctx context.Context, root string) (snapshot.Snapshotter, func(), error), fn func(ctx context.Context, t *testing.T, snapshotter snapshot.Snapshotter, work string)) func(t *testing.T) {
 	return func(t *testing.T) {
+		ctx := context.Background()
 		oldumask := syscall.Umask(0)
 		defer syscall.Umask(oldumask)
 		// Make two directories: a snapshotter root and a play area for the tests:
@@ -46,7 +47,7 @@ func makeTest(t *testing.T, name string, snapshotterFn func(root string) (snapsh
 			t.Fatal(err)
 		}
 
-		snapshotter, cleanup, err := snapshotterFn(root)
+		snapshotter, cleanup, err := snapshotterFn(ctx, root)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -58,14 +59,12 @@ func makeTest(t *testing.T, name string, snapshotterFn func(root string) (snapsh
 		}
 
 		defer testutil.DumpDir(t, tmpDir)
-		fn(t, snapshotter, work)
+		fn(ctx, t, snapshotter, work)
 	}
 }
 
 // checkSnapshotterBasic tests the basic workflow of a snapshot snapshotter.
-func checkSnapshotterBasic(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+func checkSnapshotterBasic(ctx context.Context, t *testing.T, snapshotter snapshot.Snapshotter, work string) {
-	ctx := context.TODO()
-
 	initialApplier := fstest.Apply(
 		fstest.CreateFile("/foo", []byte("foo\n"), 0777),
 		fstest.CreateDir("/a", 0755),
@@ -189,11 +188,15 @@ func checkSnapshotterBasic(t *testing.T, snapshotter snapshot.Snapshotter, work
 		fstest.Apply(initialApplier, diffApplier)); err != nil {
 		t.Fatalf("failure reason: %+v", err)
 	}
+
+	// TODO: check after remove implemented
+	//assert.Error(t, snapshotter.Remove(ctx, committed))
+	//assert.NoError(t, snapshotter.Remove(ctx, nextCommitted))
+	//assert.NoError(t, snapshotter.Remove(ctx, committed))
 }
 
 // Create a New Layer on top of base layer with Prepare, Stat on new layer, should return Active layer.
-func checkSnapshotterStatActive(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+func checkSnapshotterStatActive(ctx context.Context, t *testing.T, snapshotter snapshot.Snapshotter, work string) {
-	ctx := context.TODO()
 	preparing := filepath.Join(work, "preparing")
 	if err := os.MkdirAll(preparing, 0777); err != nil {
 		t.Fatal(err)
@@ -227,8 +230,7 @@ func checkSnapshotterStatActive(t *testing.T, snapshotter snapshot.Snapshotter,
 }
 
 // Commit a New Layer on top of base layer with Prepare & Commit , Stat on new layer, should return Committed layer.
-func checkSnapshotterStatCommitted(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+func checkSnapshotterStatCommitted(ctx context.Context, t *testing.T, snapshotter snapshot.Snapshotter, work string) {
-	ctx := context.TODO()
 	preparing := filepath.Join(work, "preparing")
 	if err := os.MkdirAll(preparing, 0777); err != nil {
 		t.Fatal(err)
@@ -289,8 +291,7 @@ func snapshotterPrepareMount(ctx context.Context, snapshotter snapshot.Snapshott
 }
 
 // Given A <- B <- C, B is the parent of C and A is a transitive parent of C (in this case, a "grandparent")
-func checkSnapshotterTransitivity(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+func checkSnapshotterTransitivity(ctx context.Context, t *testing.T, snapshotter snapshot.Snapshotter, work string) {
-	ctx := context.TODO()
 	preparing, err := snapshotterPrepareMount(ctx, snapshotter, "preparing", "", work)
 	if err != nil {
 		t.Fatal(err)
@@ -344,9 +345,7 @@ func checkSnapshotterTransitivity(t *testing.T, snapshotter snapshot.Snapshotter
 }
 
 // Creating two layers with Prepare or View with same key must fail.
-func checkSnapshotterPrepareView(t *testing.T, snapshotter snapshot.Snapshotter, work string) {
+func checkSnapshotterPrepareView(ctx context.Context, t *testing.T, snapshotter snapshot.Snapshotter, work string) {
-	ctx := context.TODO()
-
 	preparing, err := snapshotterPrepareMount(ctx, snapshotter, "preparing", "", work)
 	if err != nil {
 		t.Fatal(err)