Remove ref counting from layer store

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

layer/layer_store.go

@@ -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 := ls.mounts[l.Name()]; !ok {
-	if !ok {
 		return ErrMountDoesNotExist
 	}
-
-	if err := m.incActivityCount(l); err != nil {
-		return err
-	}
-
 	return nil
 }
 

layer/layer_test.go

@@ -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()

layer/migration_test.go

@@ -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)
 	}

layer/mounted_layer.go

@@ -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 := ml.references[ref]; !ok {
-	if !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()
+	return rl.mountedLayer.Mount(mountLabel)
-	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
 }
 
 // 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()
 }