// Returns the volume serial number of the file or directory at fsPath.
func statVolumeSerialNumber(fsPath string) (uint32, error) {
        pathp, err := syscall.UTF16PtrFromString(fsPath)
        if err != nil {
                return 0, err
        }
        h, err := syscall.CreateFile(pathp, 0, 0, nil, syscall.OPEN_EXISTING, syscall.FILE_FLAG_BACKUP_SEMANTICS, 0)
        if err != nil {
                return 0, err
        }
        defer syscall.CloseHandle(h)
        var i syscall.ByHandleFileInformation
        if err = syscall.GetFileInformationByHandle(h, &i); err != nil {
                return 0, err
        }
        return i.VolumeSerialNumber, nil
}

// sameMount reports whether childInfo and parentInfo describe
// the same file or directory in the same mount. For example,
// on Unix this means that the device fields of the two underlying
// structures are identical; on other systems the decision may
// be based on the path names. sameMount only applies to results
// returned by os.Stat. It returns false in other cases.
func sameMount(childInfo os.FileInfo, childPath string, parentInfo os.FileInfo, parentPath string) bool {
        if childInfo == nil || parentInfo == nil {
                return false
        }
        if childPath == "" || parentPath == "" {
                return false
        }
        vol1, err := statVolumeSerialNumber(childPath)
        if err != nil {
                return false
        }
        vol2, err := statVolumeSerialNumber(parentPath)
        if err != nil {
                return false
        }
        return vol1 == vol2
}