code: func getUnprivilegedMountFlags(path string) ([]string, error) {
  	var statfs unix.Statfs_t
  	if err := unix.Statfs(path, &statfs); err != nil {
  		return nil, err
  	}
  
  	// The set of keys come from https://github.com/torvalds/linux/blob/v4.13/fs/namespace.c#L1034-L1048.
  	unprivilegedFlags := map[uint64]string{
  		unix.MS_RDONLY:     "ro",
  		unix.MS_NODEV:      "nodev",
  		unix.MS_NOEXEC:     "noexec",
  		unix.MS_NOSUID:     "nosuid",
  		unix.MS_NOATIME:    "noatime",
  		unix.MS_RELATIME:   "relatime",
  		unix.MS_NODIRATIME: "nodiratime",
  	}
  
  	var flags []string
  	for mask, flag := range unprivilegedFlags {
  		if uint64(statfs.Flags)&mask == mask {
  			flags = append(flags, flag)
  		}
  	}
  
  	return flags, nil
  }
docs: // Get the set of mount flags that are set on the mount that contains the given
  // path and are locked by CL_UNPRIVILEGED. This is necessary to ensure that
  // bind-mounting "with options" will not fail with user namespaces, due to
  // kernel restrictions that require user namespace mounts to preserve
  // CL_UNPRIVILEGED locked flags.