Ensure IsSymlink works on Windows mount point

Author: laozc

pkg/os/filesystem/api.go

@@ -112,13 +112,18 @@ func (filesystemAPI) IsSymlink(tgt string) (bool, error) {
 	// This code is similar to k8s.io/kubernetes/pkg/util/mount except the pathExists usage.
 	// Also in a remote call environment the os error cannot be passed directly back, hence the callers
 	// are expected to perform the isExists check before calling this call in CSI proxy.
-	stat, err := os.Lstat(tgt)
+	isSymlink, err := utils.IsPathSymlink(tgt)
 	if err != nil {
 		return false, err
 	}
 
-	// If its a link and it points to an existing file then its a mount point.
-	if stat.Mode()&os.ModeSymlink != 0 {
+	// mounted folder created by SetVolumeMountPoint may still report ModeSymlink == 0
+	mountedFolder, err := utils.IsMountedFolder(tgt)
+	if err != nil {
+		return false, err
+	}
+
+	if isSymlink || mountedFolder {
 		target, err := os.Readlink(tgt)
 		if err != nil {
 			return false, fmt.Errorf("readlink error: %v", err)