This is an update that allows the iscsi volume to check if a iscsi device belongs to a mpio device

If it does belong to the device then we make sure we mount the mpio device instead of
the raw device.

Heuristics
Login into /dev/disk/by-path/iqn-example.com.2999 -> /dev/sde
Check if sde existsin in /sys/block/[dm-X]/slaves/xx
If it does mount /dev/[dm-x] which will look like /dev/mapper/mpiodevicename in mount

examples/iscsi has more details

pkg/volume/util/device_util_linux.go

@@ -0,0 +1,61 @@
+// +build linux
+
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+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 util
+
+import (
+	"errors"
+	"strings"
+)
+
+// FindMultipathDeviceForDevice given a device name like /dev/sdx, find the devicemapper parent
+func (handler *deviceHandler) FindMultipathDeviceForDevice(device string) string {
+	io := handler.get_io
+	disk, err := findDeviceForPath(device, io)
+	if err != nil {
+		return ""
+	}
+	sysPath := "/sys/block/"
+	if dirs, err := io.ReadDir(sysPath); err == nil {
+		for _, f := range dirs {
+			name := f.Name()
+			if strings.HasPrefix(name, "dm-") {
+				if _, err1 := io.Lstat(sysPath + name + "/slaves/" + disk); err1 == nil {
+					return "/dev/" + name
+				}
+			}
+		}
+	}
+	return ""
+}
+
+// findDeviceForPath Find the underlaying disk for a linked path such as /dev/disk/by-path/XXXX or /dev/mapper/XXXX
+// will return sdX or hdX etc, if /dev/sdX is passed in then sdX will be returned
+func findDeviceForPath(path string, io IoUtil) (string, error) {
+	devicePath, err := io.EvalSymlinks(path)
+	if err != nil {
+		return "", err
+	}
+	// if path /dev/hdX split into "", "dev", "hdX" then we will
+	// return just the last part
+	parts := strings.Split(devicePath, "/")
+	if len(parts) == 3 && strings.HasPrefix(parts[1], "dev") {
+		return parts[2], nil
+	}
+	return "", errors.New("Illegal path for device " + devicePath)
+}