github.com/sshnaidm/storage@v1.12.13/drivers/vfs/driver.go

package vfs

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/containers/storage/drivers"
	"github.com/containers/storage/pkg/idtools"
	"github.com/containers/storage/pkg/ostree"
	"github.com/containers/storage/pkg/system"
	"github.com/opencontainers/selinux/go-selinux/label"
)

var (
	// CopyDir defines the copy method to use.
	CopyDir = dirCopy
)

func init() {
	graphdriver.Register("vfs", Init)
}

// Init returns a new VFS driver.
// This sets the home directory for the driver and returns NaiveDiffDriver.
func Init(home string, options graphdriver.Options) (graphdriver.Driver, error) {
	d := &Driver{
		homes:      []string{home},
		idMappings: idtools.NewIDMappingsFromMaps(options.UIDMaps, options.GIDMaps),
	}
	rootIDs := d.idMappings.RootPair()
	if err := idtools.MkdirAllAndChown(home, 0700, rootIDs); err != nil {
		return nil, err
	}
	for _, option := range options.DriverOptions {
		if strings.HasPrefix(option, "vfs.imagestore=") {
			d.homes = append(d.homes, strings.Split(option[15:], ",")...)
			continue
		}
		if strings.HasPrefix(option, ".imagestore=") {
			d.homes = append(d.homes, strings.Split(option[12:], ",")...)
			continue
		}
		if strings.HasPrefix(option, "vfs.ostree_repo=") {
			if !ostree.OstreeSupport() {
				return nil, fmt.Errorf("vfs: ostree_repo specified but support for ostree is missing")
			}
			d.ostreeRepo = option[16:]
		}
		if strings.HasPrefix(option, ".ostree_repo=") {
			if !ostree.OstreeSupport() {
				return nil, fmt.Errorf("vfs: ostree_repo specified but support for ostree is missing")
			}
			d.ostreeRepo = option[13:]
		}
		if strings.HasPrefix(option, "vfs.mountopt=") {
			return nil, fmt.Errorf("vfs driver does not support mount options")
		}
	}
	if d.ostreeRepo != "" {
		rootUID, rootGID, err := idtools.GetRootUIDGID(options.UIDMaps, options.GIDMaps)
		if err != nil {
			return nil, err
		}
		if err := ostree.CreateOSTreeRepository(d.ostreeRepo, rootUID, rootGID); err != nil {
			return nil, err
		}
	}
	return graphdriver.NewNaiveDiffDriver(d, graphdriver.NewNaiveLayerIDMapUpdater(d)), nil
}

// Driver holds information about the driver, home directory of the driver.
// Driver implements graphdriver.ProtoDriver. It uses only basic vfs operations.
// In order to support layering, files are copied from the parent layer into the new layer. There is no copy-on-write support.
// Driver must be wrapped in NaiveDiffDriver to be used as a graphdriver.Driver
type Driver struct {
	homes      []string
	idMappings *idtools.IDMappings
	ostreeRepo string
}

func (d *Driver) String() string {
	return "vfs"
}

// Status is used for implementing the graphdriver.ProtoDriver interface. VFS does not currently have any status information.
func (d *Driver) Status() [][2]string {
	return nil
}

// Metadata is used for implementing the graphdriver.ProtoDriver interface. VFS does not currently have any meta data.
func (d *Driver) Metadata(id string) (map[string]string, error) {
	return nil, nil
}

// Cleanup is used to implement graphdriver.ProtoDriver. There is no cleanup required for this driver.
func (d *Driver) Cleanup() error {
	return nil
}

// CreateFromTemplate creates a layer with the same contents and parent as another layer.
func (d *Driver) CreateFromTemplate(id, template string, templateIDMappings *idtools.IDMappings, parent string, parentIDMappings *idtools.IDMappings, opts *graphdriver.CreateOpts, readWrite bool) error {
	if readWrite {
		return d.CreateReadWrite(id, template, opts)
	}
	return d.Create(id, template, opts)
}

// CreateReadWrite creates a layer that is writable for use as a container
// file system.
func (d *Driver) CreateReadWrite(id, parent string, opts *graphdriver.CreateOpts) error {
	return d.create(id, parent, opts, false)
}

// Create prepares the filesystem for the VFS driver and copies the directory for the given id under the parent.
func (d *Driver) Create(id, parent string, opts *graphdriver.CreateOpts) error {
	return d.create(id, parent, opts, true)
}

func (d *Driver) create(id, parent string, opts *graphdriver.CreateOpts, ro bool) error {
	if opts != nil && len(opts.StorageOpt) != 0 {
		return fmt.Errorf("--storage-opt is not supported for vfs")
	}

	idMappings := d.idMappings
	if opts != nil && opts.IDMappings != nil {
		idMappings = opts.IDMappings
	}

	dir := d.dir(id)
	rootIDs := idMappings.RootPair()
	if err := idtools.MkdirAllAndChown(filepath.Dir(dir), 0700, rootIDs); err != nil {
		return err
	}
	if parent != "" {
		st, err := system.Stat(d.dir(parent))
		if err != nil {
			return err
		}
		rootIDs.UID = int(st.UID())
		rootIDs.GID = int(st.GID())
	}
	if err := idtools.MkdirAndChown(dir, 0755, rootIDs); err != nil {
		return err
	}
	labelOpts := []string{"level:s0"}
	if _, mountLabel, err := label.InitLabels(labelOpts); err == nil {
		label.SetFileLabel(dir, mountLabel)
	}
	if parent != "" {
		parentDir, err := d.Get(parent, graphdriver.MountOpts{})
		if err != nil {
			return fmt.Errorf("%s: %s", parent, err)
		}
		if err := dirCopy(parentDir, dir); err != nil {
			return err
		}
	}

	if ro && d.ostreeRepo != "" {
		if err := ostree.ConvertToOSTree(d.ostreeRepo, dir, id); err != nil {
			return err
		}
	}
	return nil

}

func (d *Driver) dir(id string) string {
	for i, home := range d.homes {
		if i > 0 {
			home = filepath.Join(home, d.String())
		}
		candidate := filepath.Join(home, "dir", filepath.Base(id))
		fi, err := os.Stat(candidate)
		if err == nil && fi.IsDir() {
			return candidate
		}
	}
	return filepath.Join(d.homes[0], "dir", filepath.Base(id))
}

// Remove deletes the content from the directory for a given id.
func (d *Driver) Remove(id string) error {
	if d.ostreeRepo != "" {
		// Ignore errors, we don't want to fail if the ostree branch doesn't exist,
		ostree.DeleteOSTree(d.ostreeRepo, id)
	}
	return system.EnsureRemoveAll(d.dir(id))
}

// Get returns the directory for the given id.
func (d *Driver) Get(id string, options graphdriver.MountOpts) (_ string, retErr error) {
	dir := d.dir(id)
	if len(options.Options) > 0 {
		return "", fmt.Errorf("vfs driver does not support mount options")
	}
	if st, err := os.Stat(dir); err != nil {
		return "", err
	} else if !st.IsDir() {
		return "", fmt.Errorf("%s: not a directory", dir)
	}
	return dir, nil
}

// Put is a noop for vfs that return nil for the error, since this driver has no runtime resources to clean up.
func (d *Driver) Put(id string) error {
	// The vfs driver has no runtime resources (e.g. mounts)
	// to clean up, so we don't need anything here
	return nil
}

// Exists checks to see if the directory exists for the given id.
func (d *Driver) Exists(id string) bool {
	_, err := os.Stat(d.dir(id))
	return err == nil
}

// AdditionalImageStores returns additional image stores supported by the driver
func (d *Driver) AdditionalImageStores() []string {
	if len(d.homes) > 1 {
		return d.homes[1:]
	}
	return nil
}