agent: Add support for local storage

Local storage is just a directory created inside the VM.
This will use whatever the storage driver is for the container
rootfs. This will normally be 9p, but in some cases could be
device mapper. In this case the directory will benefit from the improved
performance of device mapper.

Fixes kata-containers#524

Signed-off-by: Alex Price <aprice@atlassian.com>

device.go

@@ -31,6 +31,7 @@ const (
 	driverSCSIType      = "scsi"
 	driverNvdimmType    = "nvdimm"
 	driverEphemeralType = "ephemeral"
+	driverLocalType     = "local"
 )
 
 const (

mount.go

@@ -198,6 +198,7 @@ var storageHandlerList = map[string]storageHandler{
 	driverMmioBlkType:   virtioMmioBlkStorageHandler,
 	driverSCSIType:      virtioSCSIStorageHandler,
 	driverEphemeralType: ephemeralStorageHandler,
+	driverLocalType:     localStorageHandler,
 }
 
 func ephemeralStorageHandler(storage pb.Storage, s *sandbox) (string, error) {
@@ -215,6 +216,16 @@ func ephemeralStorageHandler(storage pb.Storage, s *sandbox) (string, error) {
 	return "", nil
 }
 
+func localStorageHandler(storage pb.Storage, s *sandbox) (string, error) {
+	s.Lock()
+	defer s.Unlock()
+	newStorage := s.setSandboxStorage(storage.MountPoint)
+	if newStorage {
+		return "", os.MkdirAll(storage.MountPoint, os.ModePerm)
+	}
+	return "", nil
+}
+
 // virtio9pStorageHandler handles the storage for 9p driver.
 func virtio9pStorageHandler(storage pb.Storage, s *sandbox) (string, error) {
 	return commonStorageHandler(storage)

mount_test.go

@@ -48,6 +48,21 @@ func TestEphemeralStorageHandlerSuccessful(t *testing.T) {
 	assert.Nil(t, err, "ephemeralStorageHandler() failed: %v", err)
 }
 
+func TestLocalStorageHandlerSuccessful(t *testing.T) {
+	skipUnlessRoot(t)
+
+	storage, err := createSafeAndFakeStorage()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer syscall.Unmount(storage.MountPoint, 0)
+	defer os.RemoveAll(storage.MountPoint)
+
+	sbs := make(map[string]*sandboxStorage)
+	_, err = localStorageHandler(storage, &sandbox{storages: sbs})
+	assert.Nil(t, err, "localStorageHandler() failed: %v", err)
+}
+
 func TestVirtio9pStorageHandlerSuccessful(t *testing.T) {
 	skipUnlessRoot(t)