@@ -502,15 +502,9 @@ func (ls *layerStore) ReinitRWLayer(l RWLayer) error {

 	ls.mountL.Lock()

 	defer ls.mountL.Unlock()

-	m, ok := ls.mounts[l.Name()]

-	if !ok {

+	if _, ok := ls.mounts[l.Name()]; !ok {

 		return ErrMountDoesNotExist

 	}

-

-	if err := m.incActivityCount(l); err != nil {

-		return err

-	}

-

 	return nil

 }

@@ -400,14 +400,11 @@ func TestStoreRestore(t *testing.T) {

 	if err := ioutil.WriteFile(filepath.Join(path, "testfile.txt"), []byte("nothing here"), 0644); err != nil {

 		t.Fatal(err)

 	}

-	assertActivityCount(t, m, 1)

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

 		t.Fatal(err)

 	}

-	assertActivityCount(t, m, 0)

-

 	ls2, err := NewStoreFromGraphDriver(ls.(*layerStore).store, ls.(*layerStore).driver)

 	if err != nil {

 		t.Fatal(err)

@@ -438,20 +435,15 @@ func TestStoreRestore(t *testing.T) {

 		t.Fatalf("Unexpected path %s, expected %s", mountPath, path)

 	}

-	assertActivityCount(t, m2, 1)

-

 	if mountPath, err := m2.Mount(""); err != nil {

 		t.Fatal(err)

 	} else if path != mountPath {

 		t.Fatalf("Unexpected path %s, expected %s", mountPath, path)

 	}

-	assertActivityCount(t, m2, 2)

 	if err := m2.Unmount(); err != nil {

 		t.Fatal(err)

 	}

-	assertActivityCount(t, m2, 1)

-

 	b, err := ioutil.ReadFile(filepath.Join(path, "testfile.txt"))

 	if err != nil {

 		t.Fatal(err)

@@ -464,8 +456,6 @@ func TestStoreRestore(t *testing.T) {

 		t.Fatal(err)

 	}

-	assertActivityCount(t, m2, 0)

-

 	if metadata, err := ls2.ReleaseRWLayer(m2); err != nil {

 		t.Fatal(err)

 	} else if len(metadata) != 0 {

@@ -674,13 +664,6 @@ func assertReferences(t *testing.T, references ...Layer) {

 	}

 }

-func assertActivityCount(t *testing.T, l RWLayer, expected int) {

-	rl := l.(*referencedRWLayer)

-	if rl.activityCount != expected {

-		t.Fatalf("Unexpected activity count %d, expected %d", rl.activityCount, expected)

-	}

-}

-

 func TestRegisterExistingLayer(t *testing.T) {

 	ls, _, cleanup := newTestStore(t)

 	defer cleanup()

@@ -380,8 +380,6 @@ func TestMountMigration(t *testing.T) {

 		Kind: archive.ChangeAdd,

 	})

-	assertActivityCount(t, rwLayer1, 1)

-

 	if _, err := ls.CreateRWLayer("migration-mount", layer1.ChainID(), "", nil, nil); err == nil {

 		t.Fatal("Expected error creating mount with same name")

 	} else if err != ErrMountNameConflict {

@@ -401,16 +399,10 @@ func TestMountMigration(t *testing.T) {

 		t.Fatal(err)

 	}

-	assertActivityCount(t, rwLayer2, 1)

-	assertActivityCount(t, rwLayer1, 1)

-

 	if _, err := rwLayer2.Mount(""); err != nil {

 		t.Fatal(err)

 	}

-	assertActivityCount(t, rwLayer2, 2)

-	assertActivityCount(t, rwLayer1, 1)

-

 	if metadata, err := ls.Release(layer1); err != nil {

 		t.Fatal(err)

 	} else if len(metadata) > 0 {

@@ -420,8 +412,6 @@ func TestMountMigration(t *testing.T) {

 	if err := rwLayer1.Unmount(); err != nil {

 		t.Fatal(err)

 	}

-	assertActivityCount(t, rwLayer2, 2)

-	assertActivityCount(t, rwLayer1, 0)

 	if _, err := ls.ReleaseRWLayer(rwLayer1); err != nil {

 		t.Fatal(err)

@@ -430,9 +420,6 @@ func TestMountMigration(t *testing.T) {

 	if err := rwLayer2.Unmount(); err != nil {

 		t.Fatal(err)

 	}

-	if _, err := ls.ReleaseRWLayer(rwLayer2); err == nil {

-		t.Fatal("Expected error deleting active mount")

-	}

 	if err := rwLayer2.Unmount(); err != nil {

 		t.Fatal(err)

 	}

@@ -2,7 +2,6 @@ package layer

 import (

 	"io"

-	"sync"

 	"github.com/docker/docker/pkg/archive"

 )

@@ -83,106 +82,30 @@ func (ml *mountedLayer) hasReferences() bool {

 	return len(ml.references) > 0

 }

-func (ml *mountedLayer) incActivityCount(ref RWLayer) error {

-	rl, ok := ml.references[ref]

-	if !ok {

-		return ErrLayerNotRetained

-	}

-

-	if err := rl.acquire(); err != nil {

-		return err

-	}

-	return nil

-}

-

 func (ml *mountedLayer) deleteReference(ref RWLayer) error {

-	rl, ok := ml.references[ref]

-	if !ok {

+	if _, ok := ml.references[ref]; !ok {

 		return ErrLayerNotRetained

 	}

-

-	if err := rl.release(); err != nil {

-		return err

-	}

 	delete(ml.references, ref)

-

 	return nil

 }

 func (ml *mountedLayer) retakeReference(r RWLayer) {

 	if ref, ok := r.(*referencedRWLayer); ok {

-		ref.activityCount = 0

 		ml.references[ref] = ref

 	}

 }

 type referencedRWLayer struct {

 	*mountedLayer

-

-	activityL     sync.Mutex

-	activityCount int

-}

-

-func (rl *referencedRWLayer) acquire() error {

-	rl.activityL.Lock()

-	defer rl.activityL.Unlock()

-

-	rl.activityCount++

-

-	return nil

-}

-

-func (rl *referencedRWLayer) release() error {

-	rl.activityL.Lock()

-	defer rl.activityL.Unlock()

-

-	if rl.activityCount > 0 {

-		return ErrActiveMount

-	}

-

-	rl.activityCount = -1

-

-	return nil

 }

 func (rl *referencedRWLayer) Mount(mountLabel string) (string, error) {

-	rl.activityL.Lock()

-	defer rl.activityL.Unlock()

-

-	if rl.activityCount == -1 {

-		return "", ErrLayerNotRetained

-	}

-

-	if rl.activityCount > 0 {

-		rl.activityCount++

-		return rl.path, nil

-	}

-

-	m, err := rl.mountedLayer.Mount(mountLabel)

-	if err == nil {

-		rl.activityCount++

-		rl.path = m

-	}

-	return m, err

+	return rl.mountedLayer.Mount(mountLabel)

 }

 // Unmount decrements the activity count and unmounts the underlying layer

 // Callers should only call `Unmount` once per call to `Mount`, even on error.

 func (rl *referencedRWLayer) Unmount() error {

-	rl.activityL.Lock()

-	defer rl.activityL.Unlock()

-

-	if rl.activityCount == 0 {

-		return ErrNotMounted

-	}

-	if rl.activityCount == -1 {

-		return ErrLayerNotRetained

-	}

-

-	rl.activityCount--

-	if rl.activityCount > 0 {

-		return nil

-	}

-

 	return rl.mountedLayer.Unmount()

 }