Azure disk: dealing with missing disk probe

Signed-off-by: Huamin Chen <hchen@redhat.com>

pkg/volume/azure_dd/vhd_util.go

@@ -31,6 +31,7 @@ import (
 type ioHandler interface {
 	ReadDir(dirname string) ([]os.FileInfo, error)
 	WriteFile(filename string, data []byte, perm os.FileMode) error
+	Readlink(name string) (string, error)
 }
 
 type osIOHandler struct{}
@@ -41,56 +42,83 @@ func (handler *osIOHandler) ReadDir(dirname string) ([]os.FileInfo, error) {
 func (handler *osIOHandler) WriteFile(filename string, data []byte, perm os.FileMode) error {
 	return ioutil.WriteFile(filename, data, perm)
 }
+func (handler *osIOHandler) Readlink(name string) (string, error) {
+	return os.Readlink(name)
+}
 
-// given a LUN find the VHD device path like /dev/sdb
-// VHD disks under sysfs are like /sys/bus/scsi/devices/3:0:1:0
-// return empty string if no disk is found
+// exclude those used by azure as resource and OS root in /dev/disk/azure
+func listAzureDiskPath(io ioHandler) []string {
+	azureDiskPath := "/dev/disk/azure/"
+	var azureDiskList []string
+	if dirs, err := io.ReadDir(azureDiskPath); err == nil {
+		for _, f := range dirs {
+			name := f.Name()
+			diskPath := azureDiskPath + name
+			if link, linkErr := io.Readlink(diskPath); linkErr == nil {
+				sd := link[(strings.LastIndex(link, "/") + 1):]
+				azureDiskList = append(azureDiskList, sd)
+			}
+		}
+	}
+	glog.V(12).Infof("Azure sys disks paths: %v", azureDiskList)
+	return azureDiskList
+}
+
+// given a LUN find the VHD device path like /dev/sdd
+// exclude those disks used by Azure resources and OS root
 func findDiskByLun(lun int, io ioHandler, exe exec.Interface) (string, error) {
+	azureDisks := listAzureDiskPath(io)
+	return findDiskByLunWithConstraint(lun, io, exe, azureDisks)
+}
+
+// look for device /dev/sdX and validate it is a VHD
+// return empty string if no disk is found
+func findDiskByLunWithConstraint(lun int, io ioHandler, exe exec.Interface, azureDisks []string) (string, error) {
 	var err error
 	sys_path := "/sys/bus/scsi/devices"
 	if dirs, err := io.ReadDir(sys_path); err == nil {
 		for _, f := range dirs {
 			name := f.Name()
-			// look for path like /sys/bus/scsi/devices/3:0:1:0
+			// look for path like /sys/bus/scsi/devices/3:0:0:1
 			arr := strings.Split(name, ":")
 			if len(arr) < 4 {
 				continue
 			}
-			target, err := strconv.Atoi(arr[0])
+			// extract LUN from the path.
+			// LUN is the last index of the array, i.e. 1 in /sys/bus/scsi/devices/3:0:0:1
+			l, err := strconv.Atoi(arr[3])
 			if err != nil {
-				glog.Errorf("failed to parse target from %v (%v), err %v", arr[0], name, err)
+				// unknown path format, continue to read the next one
+				glog.Errorf("failed to parse lun from %v (%v), err %v", arr[3], name, err)
 				continue
 			}
-
-			// as observed, targets 0-3 are used by OS disks. Skip them
-			if target > 3 {
-				l, err := strconv.Atoi(arr[3])
+			if lun == l {
+				// find the matching LUN
+				// read vendor and model to ensure it is a VHD disk
+				vendor := path.Join(sys_path, name, "vendor")
+				model := path.Join(sys_path, name, "model")
+				out, err := exe.Command("cat", vendor, model).CombinedOutput()
 				if err != nil {
-					// unknown path format, continue to read the next one
-					glog.Errorf("failed to parse lun from %v (%v), err %v", arr[3], name, err)
+					glog.Errorf("failed to cat device vendor and model, err: %v", err)
 					continue
 				}
-				if lun == l {
-					// find the matching LUN
-					// read vendor and model to ensure it is a VHD disk
-					vendor := path.Join(sys_path, name, "vendor")
-					model := path.Join(sys_path, name, "model")
-					out, err := exe.Command("cat", vendor, model).CombinedOutput()
-					if err != nil {
-						glog.Errorf("failed to cat device vendor and model, err: %v", err)
-						continue
+				matched, err := regexp.MatchString("^MSFT[ ]{0,}\nVIRTUAL DISK[ ]{0,}\n$", strings.ToUpper(string(out)))
+				if err != nil || !matched {
+					glog.V(4).Infof("doesn't match VHD, output %v, error %v", string(out), err)
+					continue
+				}
+				// find a disk, validate name
+				dir := path.Join(sys_path, name, "block")
+				if dev, err := io.ReadDir(dir); err == nil {
+					found := false
+					for _, diskName := range azureDisks {
+						glog.V(12).Infof("validating disk %q with sys disk %q", dev[0].Name(), diskName)
+						if string(dev[0].Name()) == diskName {
+							found = true
+							break
+						}
 					}
-					matched, err := regexp.MatchString("^MSFT[ ]{0,}\nVIRTUAL DISK[ ]{0,}\n$", strings.ToUpper(string(out)))
-					if err != nil || !matched {
-						glog.V(4).Infof("doesn't match VHD, output %v, error %v", string(out), err)
-						continue
-					}
-					// find it!
-					dir := path.Join(sys_path, name, "block")
-					dev, err := io.ReadDir(dir)
-					if err != nil {
-						glog.Errorf("failed to read %s", dir)
-					} else {
+					if !found {
 						return "/dev/" + dev[0].Name(), nil
 					}
 				}