@@ -208,7 +208,6 @@ func (br *buildRouter) postBuild(ctx context.Context, w http.ResponseWriter, r *

 			output.Write(notVerboseBuffer.Bytes())

 		}

-		logrus.Debugf("isflushed %v", output.Flushed())

 		// Do not write the error in the http output if it's still empty.

 		// This prevents from writing a 200(OK) when there is an internal error.

 		if !output.Flushed() {

@@ -245,21 +245,23 @@ func (s *snapshotter) Mounts(ctx context.Context, key string) (snapshot.Mountabl

 	}

 	if l != nil {

 		id := identity.NewID()

-		rwlayer, err := s.opt.LayerStore.CreateRWLayer(id, l.ChainID(), nil)

-		if err != nil {

-			return nil, err

-		}

-		rootfs, err := rwlayer.Mount("")

-		if err != nil {

-			return nil, err

-		}

-		mnt := []mount.Mount{{

-			Source:  rootfs.Path(),

-			Type:    "bind",

-			Options: []string{"rbind"},

-		}}

-		return &constMountable{

-			mounts: mnt,

+		var rwlayer layer.RWLayer

+		return &mountable{

+			acquire: func() ([]mount.Mount, error) {

+				rwlayer, err = s.opt.LayerStore.CreateRWLayer(id, l.ChainID(), nil)

+				if err != nil {

+					return nil, err

+				}

+				rootfs, err := rwlayer.Mount("")

+				if err != nil {

+					return nil, err

+				}

+				return []mount.Mount{{

+					Source:  rootfs.Path(),

+					Type:    "bind",

+					Options: []string{"rbind"},

+				}}, nil

+			},

 			release: func() error {

 				_, err := s.opt.LayerStore.ReleaseRWLayer(rwlayer)

 				return err

@@ -269,17 +271,18 @@ func (s *snapshotter) Mounts(ctx context.Context, key string) (snapshot.Mountabl

 	id, _ := s.getGraphDriverID(key)

-	rootfs, err := s.opt.GraphDriver.Get(id, "")

-	if err != nil {

-		return nil, err

-	}

-	mnt := []mount.Mount{{

-		Source:  rootfs.Path(),

-		Type:    "bind",

-		Options: []string{"rbind"},

-	}}

-	return &constMountable{

-		mounts: mnt,

+	return &mountable{

+		acquire: func() ([]mount.Mount, error) {

+			rootfs, err := s.opt.GraphDriver.Get(id, "")

+			if err != nil {

+				return nil, err

+			}

+			return []mount.Mount{{

+				Source:  rootfs.Path(),

+				Type:    "bind",

+				Options: []string{"rbind"},

+			}}, nil

+		},

 		release: func() error {

 			return s.opt.GraphDriver.Put(id)

 		},

@@ -428,18 +431,37 @@ func (s *snapshotter) Close() error {

 	return s.db.Close()

 }

-type constMountable struct {

+type mountable struct {

+	mu      sync.Mutex

 	mounts  []mount.Mount

+	acquire func() ([]mount.Mount, error)

 	release func() error

 }

-func (m *constMountable) Mount() ([]mount.Mount, error) {

+func (m *mountable) Mount() ([]mount.Mount, error) {

+	m.mu.Lock()

+	defer m.mu.Unlock()

+

+	if m.mounts != nil {

+		return m.mounts, nil

+	}

+

+	mounts, err := m.acquire()

+	if err != nil {

+		return nil, err

+	}

+	m.mounts = mounts

+

 	return m.mounts, nil

 }

-func (m *constMountable) Release() error {

+func (m *mountable) Release() error {

+	m.mu.Lock()

+	defer m.mu.Unlock()

 	if m.release == nil {

 		return nil

 	}

+

+	m.mounts = nil

 	return m.release()

 }