Change globalMapPath to bind mount from symlink

This change is needed to make descriptor lock per pod, in the next commit.
If losetup is called for symlink, path in the output for losetup is resolved,
as a result, we can't distinguish which path the lock is taken.

pkg/volume/util/volumepathhandler/volume_path_handler_linux.go

@@ -19,12 +19,15 @@ limitations under the License.
 package volumepathhandler
 
 import (
+	"bufio"
 	"errors"
 	"fmt"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 
+	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/klog"
 )
 
@@ -64,7 +67,7 @@ func (v VolumePathHandler) GetLoopDevice(path string) (string, error) {
 		klog.V(2).Infof("Failed device discover command for path %s: %v %s", path, err, out)
 		return "", err
 	}
-	return parseLosetupOutputForDevice(out)
+	return parseLosetupOutputForDevice(out, path)
 }
 
 func makeLoopDevice(path string) (string, error) {
@@ -75,7 +78,14 @@ func makeLoopDevice(path string) (string, error) {
 		klog.V(2).Infof("Failed device create command for path: %s %v %s ", path, err, out)
 		return "", err
 	}
-	return parseLosetupOutputForDevice(out)
+
+	// losetup -f --show {path} returns device in the format:
+	// /dev/loop1
+	if len(out) == 0 {
+		return "", errors.New(ErrDeviceNotFound)
+	}
+
+	return strings.TrimSpace(string(out)), nil
 }
 
 // RemoveLoopDevice removes specified loopback device
@@ -93,16 +103,97 @@ func (v VolumePathHandler) RemoveLoopDevice(device string) error {
 	return nil
 }
 
-func parseLosetupOutputForDevice(output []byte) (string, error) {
+func parseLosetupOutputForDevice(output []byte, path string) (string, error) {
 	if len(output) == 0 {
 		return "", errors.New(ErrDeviceNotFound)
 	}
 
-	// losetup returns device in the format:
-	// /dev/loop1: [0073]:148662 (/dev/sda)
-	device := strings.TrimSpace(strings.SplitN(string(output), ":", 2)[0])
+	// losetup -j {path} returns device in the format:
+	// /dev/loop1: [0073]:148662 (/dev/{globalMapPath}/{pod1-UUID})
+	// /dev/loop2: [0073]:148662 (/dev/{globalMapPath}/{pod2-UUID})
+	s := string(output)
+	// Find line that exact matches the path
+	var matched string
+	scanner := bufio.NewScanner(strings.NewReader(s))
+	for scanner.Scan() {
+		if strings.HasSuffix(scanner.Text(), "("+path+")") {
+			matched = scanner.Text()
+			break
+		}
+	}
+	if len(matched) == 0 {
+		return "", errors.New(ErrDeviceNotFound)
+	}
+	s = matched
+
+	device := strings.TrimSpace(strings.SplitN(s, ":", 2)[0])
 	if len(device) == 0 {
 		return "", errors.New(ErrDeviceNotFound)
 	}
 	return device, nil
 }
+
+// FindGlobalMapPathUUIDFromPod finds {pod uuid} bind mount under globalMapPath
+// corresponding to map path symlink, and then return global map path with pod uuid.
+// ex. mapPath symlink: pods/{podUid}}/{DefaultKubeletVolumeDevicesDirName}/{escapeQualifiedPluginName}/{volumeName} -> /dev/sdX
+//     globalMapPath/{pod uuid} bind mount: plugins/kubernetes.io/{PluginName}/{DefaultKubeletVolumeDevicesDirName}/{volumePluginDependentPath}/{pod uuid} -> /dev/sdX
+func (v VolumePathHandler) FindGlobalMapPathUUIDFromPod(pluginDir, mapPath string, podUID types.UID) (string, error) {
+	var globalMapPathUUID string
+	// Find symbolic link named pod uuid under plugin dir
+	err := filepath.Walk(pluginDir, func(path string, fi os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if (fi.Mode()&os.ModeDevice == os.ModeDevice) && (fi.Name() == string(podUID)) {
+			klog.V(5).Infof("FindGlobalMapPathFromPod: path %s, mapPath %s", path, mapPath)
+			if res, err := compareBindMountAndSymlinks(path, mapPath); err == nil && res {
+				globalMapPathUUID = path
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return "", err
+	}
+	klog.V(5).Infof("FindGlobalMapPathFromPod: globalMapPathUUID %s", globalMapPathUUID)
+	// Return path contains global map path + {pod uuid}
+	return globalMapPathUUID, nil
+}
+
+func compareBindMountAndSymlinks(global, pod string) (bool, error) {
+	devNumGlobal, err := getDeviceMajorMinor(global)
+	if err != nil {
+		return false, err
+	}
+	devPod, err := os.Readlink(pod)
+	if err != nil {
+		return false, err
+	}
+	devNumPod, err := getDeviceMajorMinor(devPod)
+	if err != nil {
+		return false, err
+	}
+	klog.V(5).Infof("CompareBindMountAndSymlinks: devNumGlobal %s, devNumPod %s", devNumGlobal, devNumPod)
+	if devNumGlobal == devNumPod {
+		return true, nil
+	}
+	return false, nil
+}
+
+func getDeviceMajorMinor(path string) (string, error) {
+	args := []string{"-c", "%t:%T", path}
+	cmd := exec.Command(statPath, args...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		klog.V(2).Infof("Failed to stat path: %s %v %s ", path, err, out)
+		return "", err
+	}
+
+	// stat -c "%t:%T" {path} outputs following format(major:minor in hex):
+	// fc:10
+	if len(out) == 0 {
+		return "", errors.New(ErrDeviceNotFound)
+	}
+
+	return strings.TrimSpace(string(out)), nil
+}