return fmt.Errorf(msg, path, crossMounts)
	}
	return nil
}

// readProcMounts reads the given mountFilePath (normally /proc/mounts) and produces a hash
// of the contents.  If the out argument is not nil, this fills it with MountPoint structs.
func readProcMounts(mountFilePath string) (mountInfos, error) {
	file, err := os.Open(mountFilePath)
	if err != nil {
		return nil, err
	}

		`
	var err error
	dir := t.TempDir()
	mountsPath := filepath.Join(dir, "mounts")
	if err = os.WriteFile(mountsPath, []byte(successCase), 0o666); err != nil {
		t.Fatal(err)
	}
	mounts, err := readProcMounts(mountsPath)
	if err != nil {
		t.Fatal(err)
	}
	// Failure case where we detected successfully cross device mounts.
	{
		if err = mounts.checkCrossMounts("/path/to/1"); err == nil {