Add ImageFsInfo support

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/os/testing/fake_os.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"sync"
 
+	containerdmount "github.com/containerd/containerd/mount"
 	"github.com/docker/docker/pkg/mount"
 	"golang.org/x/net/context"
 
@@ -50,6 +51,8 @@ type FakeOS struct {
 	MountFn               func(source string, target string, fstype string, flags uintptr, data string) error
 	UnmountFn             func(target string, flags int) error
 	GetMountsFn           func() ([]*mount.Info, error)
+	LookupMountFn         func(path string) (containerdmount.Info, error)
+	DeviceUUIDFn          func(device string) (string, error)
 	calls                 []CalledDetail
 	errors                map[string]error
 }
@@ -240,3 +243,29 @@ func (f *FakeOS) GetMounts() ([]*mount.Info, error) {
 	}
 	return nil, nil
 }
+
+// LookupMount is a fake call that invokes LookupMountFn or just return nil.
+func (f *FakeOS) LookupMount(path string) (containerdmount.Info, error) {
+	f.appendCalls("LookupMount", path)
+	if err := f.getError("LookupMount"); err != nil {
+		return containerdmount.Info{}, err
+	}
+
+	if f.LookupMountFn != nil {
+		return f.LookupMountFn(path)
+	}
+	return containerdmount.Info{}, nil
+}
+
+// DeviceUUID is a fake call that invodes DeviceUUIDFn or just return nil.
+func (f *FakeOS) DeviceUUID(device string) (string, error) {
+	f.appendCalls("DeviceUUID", device)
+	if err := f.getError("DeviceUUID"); err != nil {
+		return "", err
+	}
+
+	if f.DeviceUUIDFn != nil {
+		return f.DeviceUUIDFn(device)
+	}
+	return "", nil
+}