iscsi.go

/*
Copyright 2015 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package iscsi

import (
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	"github.com/golang/glog"
	"k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/kubernetes/pkg/util/keymutex"
	"k8s.io/kubernetes/pkg/util/mount"
	utilstrings "k8s.io/kubernetes/pkg/util/strings"
	"k8s.io/kubernetes/pkg/volume"
	ioutil "k8s.io/kubernetes/pkg/volume/util"
	"k8s.io/kubernetes/pkg/volume/util/volumepathhandler"
)

// This is the primary entrypoint for volume plugins.
func ProbeVolumePlugins() []volume.VolumePlugin {
	return []volume.VolumePlugin{&iscsiPlugin{}}
}

type iscsiPlugin struct {
	host        volume.VolumeHost
	targetLocks keymutex.KeyMutex
}

var _ volume.VolumePlugin = &iscsiPlugin{}
var _ volume.PersistentVolumePlugin = &iscsiPlugin{}
var _ volume.BlockVolumePlugin = &iscsiPlugin{}

const (
	iscsiPluginName = "kubernetes.io/iscsi"
)

func (plugin *iscsiPlugin) Init(host volume.VolumeHost) error {
	plugin.host = host
	plugin.targetLocks = keymutex.NewHashed(0)
	return nil
}

func (plugin *iscsiPlugin) GetPluginName() string {
	return iscsiPluginName
}

func (plugin *iscsiPlugin) GetVolumeName(spec *volume.Spec) (string, error) {
	tp, _, iqn, lun, err := getISCSITargetInfo(spec)
	if err != nil {
		return "", err
	}

	return fmt.Sprintf("%v:%v:%v", tp, iqn, lun), nil
}

func (plugin *iscsiPlugin) CanSupport(spec *volume.Spec) bool {
	return (spec.Volume != nil && spec.Volume.ISCSI != nil) || (spec.PersistentVolume != nil && spec.PersistentVolume.Spec.ISCSI != nil)
}

func (plugin *iscsiPlugin) RequiresRemount() bool {
	return false
}

func (plugin *iscsiPlugin) SupportsMountOption() bool {
	return true
}

func (plugin *iscsiPlugin) SupportsBulkVolumeVerification() bool {
	return false
}

func (plugin *iscsiPlugin) GetAccessModes() []v1.PersistentVolumeAccessMode {
	return []v1.PersistentVolumeAccessMode{
		v1.ReadWriteOnce,
		v1.ReadOnlyMany,
	}
}

func (plugin *iscsiPlugin) NewMounter(spec *volume.Spec, pod *v1.Pod, _ volume.VolumeOptions) (volume.Mounter, error) {
	if pod == nil {
		return nil, fmt.Errorf("nil pod")
	}
	secret, err := createSecretMap(spec, plugin, pod.Namespace)
	if err != nil {
		return nil, err
	}
	return plugin.newMounterInternal(spec, pod.UID, &ISCSIUtil{}, plugin.host.GetMounter(plugin.GetPluginName()), plugin.host.GetExec(plugin.GetPluginName()), secret)
}

func (plugin *iscsiPlugin) newMounterInternal(spec *volume.Spec, podUID types.UID, manager diskManager, mounter mount.Interface, exec mount.Exec, secret map[string]string) (volume.Mounter, error) {
	readOnly, fsType, err := getISCSIVolumeInfo(spec)
	if err != nil {
		return nil, err
	}
	iscsiDisk, err := createISCSIDisk(spec, podUID, plugin, manager, secret)
	if err != nil {
		return nil, err
	}

	if iscsiDisk != nil {

		//Add volume metrics
		iscsiDisk.MetricsProvider = volume.NewMetricsStatFS(iscsiDisk.GetPath())
	}
	return &iscsiDiskMounter{
		iscsiDisk:    iscsiDisk,
		fsType:       fsType,
		readOnly:     readOnly,
		mounter:      &mount.SafeFormatAndMount{Interface: mounter, Exec: exec},
		exec:         exec,
		deviceUtil:   ioutil.NewDeviceHandler(ioutil.NewIOHandler()),
		mountOptions: ioutil.MountOptionFromSpec(spec),
	}, nil
}

// NewBlockVolumeMapper creates a new volume.BlockVolumeMapper from an API specification.
func (plugin *iscsiPlugin) NewBlockVolumeMapper(spec *volume.Spec, pod *v1.Pod, _ volume.VolumeOptions) (volume.BlockVolumeMapper, error) {
	// If this is called via GenerateUnmapDeviceFunc(), pod is nil.
	// Pass empty string as dummy uid since uid isn't used in the case.
	var uid types.UID
	var secret map[string]string
	var err error
	if pod != nil {
		uid = pod.UID
		secret, err = createSecretMap(spec, plugin, pod.Namespace)
		if err != nil {
			return nil, err
		}
	}
	return plugin.newBlockVolumeMapperInternal(spec, uid, &ISCSIUtil{}, plugin.host.GetMounter(plugin.GetPluginName()), plugin.host.GetExec(plugin.GetPluginName()), secret)
}

func (plugin *iscsiPlugin) newBlockVolumeMapperInternal(spec *volume.Spec, podUID types.UID, manager diskManager, mounter mount.Interface, exec mount.Exec, secret map[string]string) (volume.BlockVolumeMapper, error) {
	readOnly, _, err := getISCSIVolumeInfo(spec)
	if err != nil {
		return nil, err
	}
	iscsiDisk, err := createISCSIDisk(spec, podUID, plugin, manager, secret)
	if err != nil {
		return nil, err
	}
	return &iscsiDiskMapper{
		iscsiDisk:  iscsiDisk,
		readOnly:   readOnly,
		exec:       exec,
		deviceUtil: ioutil.NewDeviceHandler(ioutil.NewIOHandler()),
	}, nil
}

func (plugin *iscsiPlugin) NewUnmounter(volName string, podUID types.UID) (volume.Unmounter, error) {
	return plugin.newUnmounterInternal(volName, podUID, &ISCSIUtil{}, plugin.host.GetMounter(plugin.GetPluginName()), plugin.host.GetExec(plugin.GetPluginName()))
}

func (plugin *iscsiPlugin) newUnmounterInternal(volName string, podUID types.UID, manager diskManager, mounter mount.Interface, exec mount.Exec) (volume.Unmounter, error) {
	return &iscsiDiskUnmounter{
		iscsiDisk: &iscsiDisk{
			podUID:          podUID,
			VolName:         volName,
			manager:         manager,
			plugin:          plugin,
			MetricsProvider: volume.NewMetricsStatFS(plugin.host.GetPodVolumeDir(podUID, utilstrings.EscapeQualifiedNameForDisk(iscsiPluginName), volName)),
		},
		mounter:    mounter,
		exec:       exec,
		deviceUtil: ioutil.NewDeviceHandler(ioutil.NewIOHandler()),
	}, nil
}

// NewBlockVolumeUnmapper creates a new volume.BlockVolumeUnmapper from recoverable state.
func (plugin *iscsiPlugin) NewBlockVolumeUnmapper(volName string, podUID types.UID) (volume.BlockVolumeUnmapper, error) {
	return plugin.newUnmapperInternal(volName, podUID, &ISCSIUtil{}, plugin.host.GetExec(plugin.GetPluginName()))
}

func (plugin *iscsiPlugin) newUnmapperInternal(volName string, podUID types.UID, manager diskManager, exec mount.Exec) (volume.BlockVolumeUnmapper, error) {
	return &iscsiDiskUnmapper{
		iscsiDisk: &iscsiDisk{
			podUID:  podUID,
			VolName: volName,
			manager: manager,
			plugin:  plugin,
		},
		exec:       exec,
		deviceUtil: ioutil.NewDeviceHandler(ioutil.NewIOHandler()),
	}, nil
}

func (plugin *iscsiPlugin) ConstructVolumeSpec(volumeName, mountPath string) (*volume.Spec, error) {
	// Find globalPDPath from pod volume directory(mountPath)
	var globalPDPath string
	mounter := plugin.host.GetMounter(plugin.GetPluginName())
	paths, err := mounter.GetMountRefs(mountPath)
	if err != nil {
		return nil, err
	}
	for _, path := range paths {
		if strings.Contains(path, plugin.host.GetPluginDir(iscsiPluginName)) {
			globalPDPath = path
			break
		}
	}
	// Couldn't fetch globalPDPath
	if len(globalPDPath) == 0 {
		return nil, fmt.Errorf("couldn't fetch globalPDPath. failed to obtain volume spec")
	}

	// Obtain iscsi disk configurations from globalPDPath
	device, _, err := extractDeviceAndPrefix(globalPDPath)
	if err != nil {
		return nil, err
	}
	bkpPortal, iqn, err := extractPortalAndIqn(device)
	if err != nil {
		return nil, err
	}
	iface, _ := extractIface(globalPDPath)
	iscsiVolume := &v1.Volume{
		Name: volumeName,
		VolumeSource: v1.VolumeSource{
			ISCSI: &v1.ISCSIVolumeSource{
				TargetPortal:   bkpPortal,
				IQN:            iqn,
				ISCSIInterface: iface,
			},
		},
	}
	return volume.NewSpecFromVolume(iscsiVolume), nil
}

func (plugin *iscsiPlugin) ConstructBlockVolumeSpec(podUID types.UID, volumeName, mapPath string) (*volume.Spec, error) {
	pluginDir := plugin.host.GetVolumeDevicePluginDir(iscsiPluginName)
	blkutil := volumepathhandler.NewBlockVolumePathHandler()
	globalMapPathUUID, err := blkutil.FindGlobalMapPathUUIDFromPod(pluginDir, mapPath, podUID)
	if err != nil {
		return nil, err
	}
	glog.V(5).Infof("globalMapPathUUID: %v, err: %v", globalMapPathUUID, err)
	// Retrieve volume information from globalMapPathUUID
	// globalMapPathUUID example:
	// plugins/kubernetes.io/{PluginName}/{DefaultKubeletVolumeDevicesDirName}/{volumePluginDependentPath}/{pod uuid}
	// plugins/kubernetes.io/iscsi/volumeDevices/iface-default/192.168.0.10:3260-iqn.2017-05.com.example:test-lun-0/{pod uuid}
	globalMapPath := filepath.Dir(globalMapPathUUID)
	return getVolumeSpecFromGlobalMapPath(volumeName, globalMapPath)
}

type iscsiDisk struct {
	VolName        string
	podUID         types.UID
	Portals        []string
	Iqn            string
	Lun            string
	Iface          string
	chap_discovery bool
	chap_session   bool
	secret         map[string]string
	InitiatorName  string
	plugin         *iscsiPlugin
	// Utility interface that provides API calls to the provider to attach/detach disks.
	manager diskManager
	volume.MetricsProvider
}

func (iscsi *iscsiDisk) GetPath() string {
	name := iscsiPluginName
	// safe to use PodVolumeDir now: volume teardown occurs before pod is cleaned up
	return iscsi.plugin.host.GetPodVolumeDir(iscsi.podUID, utilstrings.EscapeQualifiedNameForDisk(name), iscsi.VolName)
}

func (iscsi *iscsiDisk) iscsiGlobalMapPath(spec *volume.Spec) (string, error) {
	mounter, err := volumeSpecToMounter(spec, iscsi.plugin.host, iscsi.plugin.targetLocks, nil /* pod */)
	if err != nil {
		glog.Warningf("failed to get iscsi mounter: %v", err)
		return "", err
	}
	return iscsi.manager.MakeGlobalVDPDName(*mounter.iscsiDisk), nil
}

func (iscsi *iscsiDisk) iscsiPodDeviceMapPath() (string, string) {
	name := iscsiPluginName
	return iscsi.plugin.host.GetPodVolumeDeviceDir(iscsi.podUID, utilstrings.EscapeQualifiedNameForDisk(name)), iscsi.VolName
}

type iscsiDiskMounter struct {
	*iscsiDisk
	readOnly     bool
	fsType       string
	volumeMode   v1.PersistentVolumeMode
	mounter      *mount.SafeFormatAndMount
	exec         mount.Exec
	deviceUtil   ioutil.DeviceUtil
	mountOptions []string
}

var _ volume.Mounter = &iscsiDiskMounter{}

func (b *iscsiDiskMounter) GetAttributes() volume.Attributes {
	return volume.Attributes{
		ReadOnly:        b.readOnly,
		Managed:         !b.readOnly,
		SupportsSELinux: true,
	}
}

// Checks prior to mount operations to verify that the required components (binaries, etc.)
// to mount the volume are available on the underlying node.
// If not, it returns an error
func (b *iscsiDiskMounter) CanMount() error {
	return nil
}

func (b *iscsiDiskMounter) SetUp(fsGroup *int64) error {
	return b.SetUpAt(b.GetPath(), fsGroup)
}

func (b *iscsiDiskMounter) SetUpAt(dir string, fsGroup *int64) error {
	// diskSetUp checks mountpoints and prevent repeated calls
	err := diskSetUp(b.manager, *b, dir, b.mounter, fsGroup)
	if err != nil {
		glog.Errorf("iscsi: failed to setup")
	}
	return err
}

type iscsiDiskUnmounter struct {
	*iscsiDisk
	mounter    mount.Interface
	exec       mount.Exec
	deviceUtil ioutil.DeviceUtil
}

var _ volume.Unmounter = &iscsiDiskUnmounter{}

// Unmounts the bind mount, and detaches the disk only if the disk
// resource was the last reference to that disk on the kubelet.
func (c *iscsiDiskUnmounter) TearDown() error {
	return c.TearDownAt(c.GetPath())
}

func (c *iscsiDiskUnmounter) TearDownAt(dir string) error {
	return ioutil.UnmountPath(dir, c.mounter)
}

// Block Volumes Support
type iscsiDiskMapper struct {
	*iscsiDisk
	readOnly   bool
	exec       mount.Exec
	deviceUtil ioutil.DeviceUtil
}

var _ volume.BlockVolumeMapper = &iscsiDiskMapper{}

func (b *iscsiDiskMapper) SetUpDevice() (string, error) {
	return "", nil
}

func (b *iscsiDiskMapper) MapDevice(devicePath, globalMapPath, volumeMapPath, volumeMapName string, podUID types.UID) error {
	return ioutil.MapBlockVolume(devicePath, globalMapPath, volumeMapPath, volumeMapName, podUID)
}

type iscsiDiskUnmapper struct {
	*iscsiDisk
	exec       mount.Exec
	deviceUtil ioutil.DeviceUtil
}

var _ volume.BlockVolumeUnmapper = &iscsiDiskUnmapper{}

// Even though iSCSI plugin has attacher/detacher implementation, iSCSI plugin
// needs volume detach operation during TearDownDevice(). This method is only
// chance that operations are done on kubelet node during volume teardown sequences.
func (c *iscsiDiskUnmapper) TearDownDevice(mapPath, _ string) error {
	err := c.manager.DetachBlockISCSIDisk(*c, mapPath)
	if err != nil {
		return fmt.Errorf("iscsi: failed to detach disk: %s\nError: %v", mapPath, err)
	}
	glog.V(4).Infof("iscsi: %q is unmounted, deleting the directory", mapPath)
	err = os.RemoveAll(mapPath)
	if err != nil {
		return fmt.Errorf("iscsi: failed to delete the directory: %s\nError: %v", mapPath, err)
	}
	glog.V(4).Infof("iscsi: successfully detached disk: %s", mapPath)
	return nil
}

// GetGlobalMapPath returns global map path and error
// path: plugins/kubernetes.io/{PluginName}/volumeDevices/{ifaceName}/{portal-some_iqn-lun-lun_id}
func (iscsi *iscsiDisk) GetGlobalMapPath(spec *volume.Spec) (string, error) {
	return iscsi.iscsiGlobalMapPath(spec)
}

// GetPodDeviceMapPath returns pod device map path and volume name
// path: pods/{podUid}/volumeDevices/kubernetes.io~iscsi
// volumeName: pv0001
func (iscsi *iscsiDisk) GetPodDeviceMapPath() (string, string) {
	return iscsi.iscsiPodDeviceMapPath()
}

func portalMounter(portal string) string {
	if !strings.Contains(portal, ":") {
		portal = portal + ":3260"
	}
	return portal
}

// get iSCSI volume info: readOnly and fstype
func getISCSIVolumeInfo(spec *volume.Spec) (bool, string, error) {
	// for volume source, readonly is in volume spec
	// for PV, readonly is in PV spec. PV gets the ReadOnly flag indirectly through the PVC source
	if spec.Volume != nil && spec.Volume.ISCSI != nil {
		return spec.Volume.ISCSI.ReadOnly, spec.Volume.ISCSI.FSType, nil
	} else if spec.PersistentVolume != nil &&
		spec.PersistentVolume.Spec.ISCSI != nil {
		return spec.ReadOnly, spec.PersistentVolume.Spec.ISCSI.FSType, nil
	}

	return false, "", fmt.Errorf("Spec does not reference an ISCSI volume type")
}

// get iSCSI target info: target portal, portals, iqn, and lun
func getISCSITargetInfo(spec *volume.Spec) (string, []string, string, int32, error) {
	if spec.Volume != nil && spec.Volume.ISCSI != nil {
		return spec.Volume.ISCSI.TargetPortal, spec.Volume.ISCSI.Portals, spec.Volume.ISCSI.IQN, spec.Volume.ISCSI.Lun, nil
	} else if spec.PersistentVolume != nil &&
		spec.PersistentVolume.Spec.ISCSI != nil {
		return spec.PersistentVolume.Spec.ISCSI.TargetPortal, spec.PersistentVolume.Spec.ISCSI.Portals, spec.PersistentVolume.Spec.ISCSI.IQN, spec.PersistentVolume.Spec.ISCSI.Lun, nil
	}

	return "", nil, "", 0, fmt.Errorf("Spec does not reference an ISCSI volume type")
}

// get iSCSI initiator info: iface and initiator name
func getISCSIInitiatorInfo(spec *volume.Spec) (string, *string, error) {
	if spec.Volume != nil && spec.Volume.ISCSI != nil {
		return spec.Volume.ISCSI.ISCSIInterface, spec.Volume.ISCSI.InitiatorName, nil
	} else if spec.PersistentVolume != nil &&
		spec.PersistentVolume.Spec.ISCSI != nil {
		return spec.PersistentVolume.Spec.ISCSI.ISCSIInterface, spec.PersistentVolume.Spec.ISCSI.InitiatorName, nil
	}

	return "", nil, fmt.Errorf("Spec does not reference an ISCSI volume type")
}

// get iSCSI Discovery CHAP boolean
func getISCSIDiscoveryCHAPInfo(spec *volume.Spec) (bool, error) {
	if spec.Volume != nil && spec.Volume.ISCSI != nil {
		return spec.Volume.ISCSI.DiscoveryCHAPAuth, nil
	} else if spec.PersistentVolume != nil &&
		spec.PersistentVolume.Spec.ISCSI != nil {
		return spec.PersistentVolume.Spec.ISCSI.DiscoveryCHAPAuth, nil
	}

	return false, fmt.Errorf("Spec does not reference an ISCSI volume type")
}

// get iSCSI Session CHAP boolean
func getISCSISessionCHAPInfo(spec *volume.Spec) (bool, error) {
	if spec.Volume != nil && spec.Volume.ISCSI != nil {
		return spec.Volume.ISCSI.SessionCHAPAuth, nil
	} else if spec.PersistentVolume != nil &&
		spec.PersistentVolume.Spec.ISCSI != nil {
		return spec.PersistentVolume.Spec.ISCSI.SessionCHAPAuth, nil
	}

	return false, fmt.Errorf("Spec does not reference an ISCSI volume type")
}

// get iSCSI CHAP Secret info: secret name and namespace
func getISCSISecretNameAndNamespace(spec *volume.Spec, defaultSecretNamespace string) (string, string, error) {
	if spec.Volume != nil && spec.Volume.ISCSI != nil {
		if spec.Volume.ISCSI.SecretRef != nil {
			return spec.Volume.ISCSI.SecretRef.Name, defaultSecretNamespace, nil
		}
		return "", "", nil
	} else if spec.PersistentVolume != nil &&
		spec.PersistentVolume.Spec.ISCSI != nil {
		secretRef := spec.PersistentVolume.Spec.ISCSI.SecretRef
		secretNs := defaultSecretNamespace
		if secretRef != nil {
			if len(secretRef.Namespace) != 0 {
				secretNs = secretRef.Namespace
			}
			return secretRef.Name, secretNs, nil
		}
		return "", "", nil
	}

	return "", "", fmt.Errorf("Spec does not reference an ISCSI volume type")
}

func createISCSIDisk(spec *volume.Spec, podUID types.UID, plugin *iscsiPlugin, manager diskManager, secret map[string]string) (*iscsiDisk, error) {
	tp, portals, iqn, lunStr, err := getISCSITargetInfo(spec)
	if err != nil {
		return nil, err
	}

	lun := strconv.Itoa(int(lunStr))
	portal := portalMounter(tp)
	var bkportal []string
	bkportal = append(bkportal, portal)
	for _, p := range portals {
		bkportal = append(bkportal, portalMounter(string(p)))
	}

	iface, initiatorNamePtr, err := getISCSIInitiatorInfo(spec)
	if err != nil {
		return nil, err
	}

	var initiatorName string
	if initiatorNamePtr != nil {
		initiatorName = *initiatorNamePtr
	}
	chapDiscovery, err := getISCSIDiscoveryCHAPInfo(spec)
	if err != nil {
		return nil, err
	}
	chapSession, err := getISCSISessionCHAPInfo(spec)
	if err != nil {
		return nil, err
	}

	return &iscsiDisk{
		podUID:         podUID,
		VolName:        spec.Name(),
		Portals:        bkportal,
		Iqn:            iqn,
		Lun:            lun,
		Iface:          iface,
		chap_discovery: chapDiscovery,
		chap_session:   chapSession,
		secret:         secret,
		InitiatorName:  initiatorName,
		manager:        manager,
		plugin:         plugin}, nil
}

func createSecretMap(spec *volume.Spec, plugin *iscsiPlugin, namespace string) (map[string]string, error) {
	var secret map[string]string
	chapDiscover, err := getISCSIDiscoveryCHAPInfo(spec)
	if err != nil {
		return nil, err
	}
	chapSession, err := getISCSISessionCHAPInfo(spec)
	if err != nil {
		return nil, err
	}
	if chapDiscover || chapSession {
		secretName, secretNamespace, err := getISCSISecretNameAndNamespace(spec, namespace)
		if err != nil {
			return nil, err
		}

		if len(secretName) > 0 && len(secretNamespace) > 0 {
			// if secret is provideded, retrieve it
			kubeClient := plugin.host.GetKubeClient()
			if kubeClient == nil {
				return nil, fmt.Errorf("Cannot get kube client")
			}
			secretObj, err := kubeClient.CoreV1().Secrets(secretNamespace).Get(secretName, metav1.GetOptions{})
			if err != nil {
				err = fmt.Errorf("Couldn't get secret %v/%v error: %v", secretNamespace, secretName, err)
				return nil, err
			}
			secret = make(map[string]string)
			for name, data := range secretObj.Data {
				glog.V(4).Infof("retrieving CHAP secret name: %s", name)
				secret[name] = string(data)
			}
		}
	}
	return secret, err
}

func createVolumeFromISCSIVolumeSource(volumeName string, iscsi v1.ISCSIVolumeSource) *v1.Volume {
	return &v1.Volume{
		Name: volumeName,
		VolumeSource: v1.VolumeSource{
			ISCSI: &iscsi,
		},
	}
}

func createPersistentVolumeFromISCSIPVSource(volumeName string, iscsi v1.ISCSIPersistentVolumeSource) *v1.PersistentVolume {
	block := v1.PersistentVolumeBlock
	return &v1.PersistentVolume{
		ObjectMeta: metav1.ObjectMeta{
			Name: volumeName,
		},
		Spec: v1.PersistentVolumeSpec{
			PersistentVolumeSource: v1.PersistentVolumeSource{
				ISCSI: &iscsi,
			},
			VolumeMode: &block,
		},
	}
}

func getVolumeSpecFromGlobalMapPath(volumeName, globalMapPath string) (*volume.Spec, error) {
	// Retrieve volume spec information from globalMapPath
	// globalMapPath example:
	// plugins/kubernetes.io/{PluginName}/{DefaultKubeletVolumeDevicesDirName}/{volumePluginDependentPath}
	// plugins/kubernetes.io/iscsi/volumeDevices/iface-default/192.168.0.10:3260-iqn.2017-05.com.example:test-lun-0

	// device: 192.168.0.10:3260-iqn.2017-05.com.example:test-lun-0
	device, _, err := extractDeviceAndPrefix(globalMapPath)
	if err != nil {
		return nil, err
	}
	bkpPortal, iqn, err := extractPortalAndIqn(device)
	if err != nil {
		return nil, err
	}
	arr := strings.Split(device, "-lun-")
	if len(arr) < 2 {
		return nil, fmt.Errorf("failed to retrieve lun from globalMapPath: %v", globalMapPath)
	}
	lun, err := strconv.Atoi(arr[1])
	if err != nil {
		return nil, err
	}
	iface, found := extractIface(globalMapPath)
	if !found {
		return nil, fmt.Errorf("failed to retrieve iface from globalMapPath: %v", globalMapPath)
	}
	iscsiPV := createPersistentVolumeFromISCSIPVSource(volumeName,
		v1.ISCSIPersistentVolumeSource{
			TargetPortal:   bkpPortal,
			IQN:            iqn,
			Lun:            int32(lun),
			ISCSIInterface: iface,
		},
	)
	glog.V(5).Infof("ConstructBlockVolumeSpec: TargetPortal: %v, IQN: %v, Lun: %v, ISCSIInterface: %v",
		iscsiPV.Spec.PersistentVolumeSource.ISCSI.TargetPortal,
		iscsiPV.Spec.PersistentVolumeSource.ISCSI.IQN,
		iscsiPV.Spec.PersistentVolumeSource.ISCSI.Lun,
		iscsiPV.Spec.PersistentVolumeSource.ISCSI.ISCSIInterface,
	)
	return volume.NewSpecFromPersistentVolume(iscsiPV, false), nil
}