Function getCommonDirectory

core/mount/mount_linux.go:305–319

getCommonDirectory finds the common directory among the lowerDirs passed in. "/" and "." are considered invalid common directories and are treated as error

(lowerDirs []string)

// getCommonDirectory finds the common directory among the lowerDirs passed in.
// "/" and "." are considered invalid common directories and are treated as error
func getCommonDirectory(lowerDirs []string) (string, error) {
	commonPrefix := longestCommonPrefix(lowerDirs)
	if commonPrefix == "" {
		return "", fmt.Errorf("no common prefix found")
	}

	// Ensure the common prefix ends at a directory boundary
	commonPrefix = path.Dir(commonPrefix)

	if commonPrefix == "." || commonPrefix == "/" {
		return "", fmt.Errorf("invalid common directory: %s", commonPrefix)
	}

	return commonPrefix, nil
}

// buildIDMappedPaths constructs new lower directory paths through an idmapped mount of the commonDir.
// It takes the original lowerDirs, the commonDir of those dirs, and rewrites the paths