@@ -14,7 +14,7 @@ import (

 type Backend interface {

 	SystemInfo() (*types.Info, error)

 	SystemVersion() types.Version

-	SystemDiskUsage() (*types.DiskUsage, error)

+	SystemDiskUsage(ctx context.Context) (*types.DiskUsage, error)

 	SubscribeToEvents(since, until time.Time, ef filters.Args) ([]events.Message, chan interface{})

 	UnsubscribeFromEvents(chan interface{})

 	AuthenticateToRegistry(ctx context.Context, authConfig *types.AuthConfig) (string, string, error)

@@ -26,7 +26,7 @@ func NewRouter(b Backend, c *cluster.Cluster) router.Router {

 		router.NewGetRoute("/events", r.getEvents, router.WithCancel),

 		router.NewGetRoute("/info", r.getInfo),

 		router.NewGetRoute("/version", r.getVersion),

-		router.NewGetRoute("/system/df", r.getDiskUsage),

+		router.NewGetRoute("/system/df", r.getDiskUsage, router.WithCancel),

 		router.NewPostRoute("/auth", r.postAuth),

 	}

@@ -71,7 +71,7 @@ func (s *systemRouter) getVersion(ctx context.Context, w http.ResponseWriter, r

 }

 func (s *systemRouter) getDiskUsage(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {

-	du, err := s.backend.SystemDiskUsage()

+	du, err := s.backend.SystemDiskUsage(ctx)

 	if err != nil {

 		return err

 	}

@@ -3,6 +3,8 @@ package daemon

 import (

 	"fmt"

+	"golang.org/x/net/context"

+

 	"github.com/Sirupsen/logrus"

 	"github.com/docker/docker/api/types"

 	"github.com/docker/docker/api/types/filters"

@@ -34,7 +36,7 @@ func (daemon *Daemon) getLayerRefs() map[layer.ChainID]int {

 }

 // SystemDiskUsage returns information about the daemon data disk usage

-func (daemon *Daemon) SystemDiskUsage() (*types.DiskUsage, error) {

+func (daemon *Daemon) SystemDiskUsage(ctx context.Context) (*types.DiskUsage, error) {

 	// Retrieve container list

 	allContainers, err := daemon.Containers(&types.ContainerListOptions{

 		Size: true,

@@ -53,17 +55,22 @@ func (daemon *Daemon) SystemDiskUsage() (*types.DiskUsage, error) {

 	// Get all local volumes

 	allVolumes := []*types.Volume{}

 	getLocalVols := func(v volume.Volume) error {

-		name := v.Name()

-		refs := daemon.volumes.Refs(v)

+		select {

+		case <-ctx.Done():

+			return ctx.Err()

+		default:

+			name := v.Name()

+			refs := daemon.volumes.Refs(v)

-		tv := volumeToAPIType(v)

-		sz, err := directory.Size(v.Path())

-		if err != nil {

-			logrus.Warnf("failed to determine size of volume %v", name)

-			sz = -1

+			tv := volumeToAPIType(v)

+			sz, err := directory.Size(v.Path())

+			if err != nil {

+				logrus.Warnf("failed to determine size of volume %v", name)

+				sz = -1

+			}

+			tv.UsageData = &types.VolumeUsageData{Size: sz, RefCount: int64(len(refs))}

+			allVolumes = append(allVolumes, tv)

 		}

-		tv.UsageData = &types.VolumeUsageData{Size: sz, RefCount: int64(len(refs))}

-		allVolumes = append(allVolumes, tv)

 		return nil

 	}

@@ -78,17 +85,21 @@ func (daemon *Daemon) SystemDiskUsage() (*types.DiskUsage, error) {

 	allLayers := daemon.layerStore.Map()

 	var allLayersSize int64

 	for _, l := range allLayers {

-		size, err := l.DiffSize()

-		if err == nil {

-			if _, ok := layerRefs[l.ChainID()]; ok {

-				allLayersSize += size

+		select {

+		case <-ctx.Done():

+			return nil, ctx.Err()

+		default:

+			size, err := l.DiffSize()

+			if err == nil {

+				if _, ok := layerRefs[l.ChainID()]; ok {

+					allLayersSize += size

+				} else {

+					logrus.Warnf("found leaked image layer %v", l.ChainID())

+				}

 			} else {

-				logrus.Warnf("found leaked image layer %v", l.ChainID())

+				logrus.Warnf("failed to get diff size for layer %v", l.ChainID())

 			}

-		} else {

-			logrus.Warnf("failed to get diff size for layer %v", l.ChainID())

 		}

-

 	}

 	return &types.DiskUsage{