Function prepareIDMappedOverlay

core/mount/mount_linux.go:59–74

prepareIDMappedOverlay is a helper function to obtain actual "lowerdir=..." mount options. It creates and applies id mapping for each lowerdir. It returns: 1. New options that include new "lowedir=..." mount option. 2. "Clean up" function -- it should be called only if no error is returned. 3. Erro

(usernsFd int, options []string)

//  2. "Clean up" function -- it should be called only if no error is returned.
//  3. Error -- nil if everything's fine, otherwise an error.
func prepareIDMappedOverlay(usernsFd int, options []string) ([]string, func(), error) {
	lowerIdx, lowerDirs := findOverlayLowerdirs(options)
	if lowerIdx == -1 {
		return options, nil, fmt.Errorf("failed to parse overlay lowerdir's from given options")
	}

	tmpLowerdirs, idMapCleanUp, err := doPrepareIDMappedOverlay(tempMountLocation, lowerDirs, usernsFd)
	if err != nil {
		return options, idMapCleanUp, fmt.Errorf("failed to create idmapped mount: %w", err)
	}

	options = append(options[:lowerIdx], options[lowerIdx+1:]...)
	options = append(options, fmt.Sprintf("lowerdir=%s", strings.Join(tmpLowerdirs, ":")))

	return options, idMapCleanUp, nil
}

// Mount to the provided target path.
//