Merge pull request #45840 from cpuguy83/20.10_fix_live_restore_local_vol_mounts

[20.10] Backport Restore active mount counts on live-restore

daemon/mounts.go

@@ -8,13 +8,24 @@ import (
 	mounttypes "github.com/docker/docker/api/types/mount"
 	"github.com/docker/docker/container"
 	volumesservice "github.com/docker/docker/volume/service"
+	"github.com/sirupsen/logrus"
 )
 
 func (daemon *Daemon) prepareMountPoints(container *container.Container) error {
+	alive := container.IsRunning()
 	for _, config := range container.MountPoints {
 		if err := daemon.lazyInitializeVolume(container.ID, config); err != nil {
 			return err
 		}
+		if alive {
+			logrus.WithFields(logrus.Fields{
+				"container": container.ID,
+				"volume":    config.Volume.Name(),
+			}).Debug("Live-restoring volume for alive container")
+			if err := config.LiveRestore(context.TODO()); err != nil {
+				return err
+			}
+		}
 	}
 	return nil
 }

daemon/volumes.go

@@ -25,7 +25,8 @@ import (
 var (
 	// ErrVolumeReadonly is used to signal an error when trying to copy data into
 	// a volume mount that is not writable.
-	ErrVolumeReadonly = errors.New("mounted volume is marked read-only")
+	ErrVolumeReadonly                     = errors.New("mounted volume is marked read-only")
+	_                 volume.LiveRestorer = (*volumeWrapper)(nil)
 )
 
 type mounts []container.Mount
@@ -387,6 +388,7 @@ func (daemon *Daemon) VolumesService() *service.VolumesService {
 type volumeMounter interface {
 	Mount(ctx context.Context, v *types.Volume, ref string) (string, error)
 	Unmount(ctx context.Context, v *types.Volume, ref string) error
+	LiveRestoreVolume(ctx context.Context, v *types.Volume, ref string) error
 }
 
 type volumeWrapper struct {
@@ -421,3 +423,7 @@ func (v *volumeWrapper) CreatedAt() (time.Time, error) {
 func (v *volumeWrapper) Status() map[string]interface{} {
 	return v.v.Status
 }
+
+func (v *volumeWrapper) LiveRestoreVolume(ctx context.Context, ref string) error {
+	return v.s.LiveRestoreVolume(ctx, v.v, ref)
+}

integration/daemon/daemon_test.go

@@ -66,4 +66,40 @@ func testLiveRestoreVolumeReferences(t *testing.T) {
 		runTest(t, "on-failure")
 		runTest(t, "no")
 	})
+
+	// Make sure that the local volume driver's mount ref count is restored
+	// Addresses https://github.com/moby/moby/issues/44422
+	t.Run("local volume with mount options", func(t *testing.T) {
+		v, err := c.VolumeCreate(ctx, volume.VolumeCreateBody{
+			Driver: "local",
+			Name:   "test-live-restore-volume-references-local",
+			DriverOpts: map[string]string{
+				"type":   "tmpfs",
+				"device": "tmpfs",
+			},
+		})
+		assert.NilError(t, err)
+		m := mount.Mount{
+			Type:   mount.TypeVolume,
+			Source: v.Name,
+			Target: "/foo",
+		}
+		cID := container.Run(ctx, t, c, container.WithMount(m), container.WithCmd("top"))
+		defer c.ContainerRemove(ctx, cID, types.ContainerRemoveOptions{Force: true})
+
+		d.Restart(t, "--live-restore", "--iptables=false")
+
+		// Try to remove the volume
+		// This should fail since its used by a container
+		err = c.VolumeRemove(ctx, v.Name, false)
+		assert.ErrorContains(t, err, "volume is in use")
+
+		// Remove that container which should free the references in the volume
+		err = c.ContainerRemove(ctx, cID, types.ContainerRemoveOptions{Force: true})
+		assert.NilError(t, err)
+
+		// Now we should be able to remove the volume
+		err = c.VolumeRemove(ctx, v.Name, false)
+		assert.NilError(t, err)
+	})
 }

volume/local/local.go

@@ -4,6 +4,7 @@
 package local // import "github.com/docker/docker/volume/local"
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"os"
@@ -36,6 +37,8 @@ var (
 	// This name is used to create the bind directory, so we need to avoid characters that
 	// would make the path to escape the root directory.
 	volumeNameRegex = names.RestrictedNamePattern
+
+	_ volume.LiveRestorer = (*localVolume)(nil)
 )
 
 type activeMount struct {
@@ -315,14 +318,17 @@ func (v *localVolume) CachedPath() string {
 func (v *localVolume) Mount(id string) (string, error) {
 	v.m.Lock()
 	defer v.m.Unlock()
+	logger := logrus.WithField("volume", v.name)
 	if v.needsMount() {
 		if !v.active.mounted {
+			logger.Debug("Mounting volume")
 			if err := v.mount(); err != nil {
 				return "", errdefs.System(err)
 			}
 			v.active.mounted = true
 		}
 		v.active.count++
+		logger.WithField("active mounts", v.active).Debug("Decremented active mount count")
 	}
 	if err := v.postMount(); err != nil {
 		return "", err
@@ -335,6 +341,7 @@ func (v *localVolume) Mount(id string) (string, error) {
 func (v *localVolume) Unmount(id string) error {
 	v.m.Lock()
 	defer v.m.Unlock()
+	logger := logrus.WithField("volume", v.name)
 
 	// Always decrement the count, even if the unmount fails
 	// Essentially docker doesn't care if this fails, it will send an error, but
@@ -342,12 +349,14 @@ func (v *localVolume) Unmount(id string) error {
 	// this volume can never be removed until a daemon restart occurs.
 	if v.needsMount() {
 		v.active.count--
+		logger.WithField("active mounts", v.active).Debug("Decremented active mount count")
 	}
 
 	if v.active.count > 0 {
 		return nil
 	}
 
+	logger.Debug("Unmounting volume")
 	return v.unmount()
 }
 
@@ -355,6 +364,24 @@ func (v *localVolume) Status() map[string]interface{} {
 	return nil
 }
 
+// LiveRestoreVolume restores reference counts for mounts
+// It is assumed that the volume is already mounted since this is only called for active, live-restored containers.
+func (v *localVolume) LiveRestoreVolume(ctx context.Context, _ string) error {
+	v.m.Lock()
+	defer v.m.Unlock()
+
+	if !v.needsMount() {
+		return nil
+	}
+	v.active.count++
+	v.active.mounted = true
+	logrus.WithFields(logrus.Fields{
+		"volume":        v.name,
+		"active mounts": v.active,
+	}).Debugf("Live restored volume")
+	return nil
+}
+
 // getAddress finds out address/hostname from options
 func getAddress(opts string) string {
 	optsList := strings.Split(opts, ",")

volume/mounts/mounts.go

@@ -1,6 +1,7 @@
 package mounts // import "github.com/docker/docker/volume/mounts"
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -12,6 +13,7 @@ import (
 	"github.com/docker/docker/volume"
 	"github.com/opencontainers/selinux/go-selinux/label"
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
 // MountPoint is the intersection point between a volume and a container. It
@@ -179,3 +181,29 @@ func errInvalidMode(mode string) error {
 func errInvalidSpec(spec string) error {
 	return errors.Errorf("invalid volume specification: '%s'", spec)
 }
+
+func (m *MountPoint) LiveRestore(ctx context.Context) error {
+	if m.Volume == nil {
+		logrus.Debug("No volume to restore")
+		return nil
+	}
+
+	lrv, ok := m.Volume.(volume.LiveRestorer)
+	if !ok {
+		logrus.WithField("volume", m.Volume.Name()).Debugf("Volume does not support live restore: %T", m.Volume)
+		return nil
+	}
+
+	id := m.ID
+	if id == "" {
+		id = stringid.GenerateRandomID()
+	}
+
+	if err := lrv.LiveRestoreVolume(ctx, id); err != nil {
+		return errors.Wrapf(err, "error while restoring volume '%s'", m.Source)
+	}
+
+	m.ID = id
+	m.active++
+	return nil
+}

volume/service/service.go

@@ -265,3 +265,18 @@ func (s *VolumesService) List(ctx context.Context, filter filters.Args) (volumes
 func (s *VolumesService) Shutdown() error {
 	return s.vs.Shutdown()
 }
+
+// LiveRestoreVolume passes through the LiveRestoreVolume call to the volume if it is implemented
+// otherwise it is a no-op.
+func (s *VolumesService) LiveRestoreVolume(ctx context.Context, vol *types.Volume, ref string) error {
+	v, err := s.vs.Get(ctx, vol.Name, opts.WithGetDriver(vol.Driver))
+	if err != nil {
+		return err
+	}
+	rlv, ok := v.(volume.LiveRestorer)
+	if !ok {
+		logrus.WithField("volume", vol.Name).Debugf("volume does not implement LiveRestoreVolume: %T", v)
+		return nil
+	}
+	return rlv.LiveRestoreVolume(ctx, ref)
+}

volume/service/store.go

@@ -25,6 +25,8 @@ const (
 	volumeDataDir = "volumes"
 )
 
+var _ volume.LiveRestorer = (*volumeWrapper)(nil)
+
 type volumeWrapper struct {
 	volume.Volume
 	labels  map[string]string
@@ -68,6 +70,13 @@ func (v volumeWrapper) CachedPath() string {
 	return v.Volume.Path()
 }
 
+func (v volumeWrapper) LiveRestoreVolume(ctx context.Context, ref string) error {
+	if vv, ok := v.Volume.(volume.LiveRestorer); ok {
+		return vv.LiveRestoreVolume(ctx, ref)
+	}
+	return nil
+}
+
 // NewStore creates a new volume store at the given path
 func NewStore(rootPath string, drivers *drivers.Store) (*VolumeStore, error) {
 	vs := &VolumeStore{

volume/volume.go

@@ -1,6 +1,7 @@
 package volume // import "github.com/docker/docker/volume"
 
 import (
+	"context"
 	"time"
 )
 
@@ -67,3 +68,12 @@ type DetailedVolume interface {
 	Scope() string
 	Volume
 }
+
+// LiveRestorer is an optional interface that can be implemented by a volume driver
+// It is used to restore any resources that are necessary for a volume to be used by a live-restored container
+type LiveRestorer interface {
+	// LiveRestoreVolume allows a volume driver which implements this interface to restore any necessary resources (such as reference counting)
+	// This is called only after the daemon is restarted with live-restored containers
+	// It is called once per live-restored container.
+	LiveRestoreVolume(_ context.Context, ref string) error
+}