fix(node): add OS-specific HasMountReferences implementations to support Windows and Darwin

Refactored NodeUnstageVolume to use a platform-aware HasMountReferences() helper,
moving Linux-specific /proc/mounts parsing into smb_common_linux.go and stubbing
it out for Windows and Darwin to prevent test failures on non-Linux environments.

- Fixes Windows e2e failures due to /proc/mounts not being available
- Ensures future compatibility for multi-platform CSI driver builds
- Preserves original Linux mount reference tracking behavior

Author: MattPOlson

pkg/smb/nodeserver.go

@@ -17,7 +17,6 @@ limitations under the License.
 package smb
 
 import (
-	"bufio"
 	"encoding/base64"
 	"fmt"
 	"os"
@@ -316,27 +315,12 @@ func (d *Driver) NodeUnstageVolume(_ context.Context, req *csi.NodeUnstageVolume
 	}
 	defer d.volumeLocks.Release(lockKey)
 
-	// Check if any other mounts still reference the staging path
-	f, err := os.Open("/proc/mounts")
+	inUse, err := HasMountReferences(stagingTargetPath)
 	if err != nil {
-		return nil, status.Errorf(codes.Internal, "failed to open /proc/mounts: %v", err)
-	}
-	defer f.Close()
-
-	scanner := bufio.NewScanner(f)
-	refCount := 0
-	for scanner.Scan() {
-		line := scanner.Text()
-		fields := strings.Fields(line)
-		if len(fields) >= 2 {
-			mountPoint := fields[1]
-			if strings.HasPrefix(mountPoint, stagingTargetPath) && mountPoint != stagingTargetPath {
-				refCount++
-			}
-		}
+		return nil, status.Errorf(codes.Internal, "failed to check mount references: %v", err)
 	}
-	if refCount > 0 {
-		klog.V(2).Infof("NodeUnstageVolume: staging path %s is still in use by %d other mounts", stagingTargetPath, refCount)
+	if inUse {
+		klog.V(2).Infof("NodeUnstageVolume: staging path %s is still in use by other mounts", stagingTargetPath)
 		return &csi.NodeUnstageVolumeResponse{}, nil
 	}
 

pkg/smb/smb_common_darwin.go

@@ -48,3 +48,8 @@ func prepareStagePath(path string, m *mount.SafeFormatAndMount) error {
 func Mkdir(m *mount.SafeFormatAndMount, name string, perm os.FileMode) error {
 	return os.Mkdir(name, perm)
 }
+
+func HasMountReferences(stagingTargetPath string) (bool, error) {
+	// Stubbed for Windows/macOS — cannot inspect bind mounts
+	return false, nil
+}

pkg/smb/smb_common_linux.go

@@ -20,7 +20,10 @@ limitations under the License.
 package smb
 
 import (
+	"bufio"
+	"fmt"
 	"os"
+	"strings"
 
 	mount "k8s.io/mount-utils"
 )
@@ -48,3 +51,23 @@ func prepareStagePath(_ string, _ *mount.SafeFormatAndMount) error {
 func Mkdir(_ *mount.SafeFormatAndMount, name string, perm os.FileMode) error {
 	return os.Mkdir(name, perm)
 }
+
+func HasMountReferences(stagingTargetPath string) (bool, error) {
+	f, err := os.Open("/proc/mounts")
+	if err != nil {
+		return false, fmt.Errorf("failed to open /proc/mounts: %v", err)
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) >= 2 {
+			mountPoint := fields[1]
+			if strings.HasPrefix(mountPoint, stagingTargetPath) && mountPoint != stagingTargetPath {
+				return true, nil
+			}
+		}
+	}
+	return false, nil
+}

pkg/smb/smb_common_windows.go

@@ -87,3 +87,8 @@ func Mkdir(m *mount.SafeFormatAndMount, name string, perm os.FileMode) error {
 	}
 	return fmt.Errorf("could not cast to csi proxy class")
 }
+
+func HasMountReferences(stagingTargetPath string) (bool, error) {
+	// Stubbed for Windows/macOS — cannot inspect bind mounts
+	return false, nil
+}