daemon/graphdriver/vfs/driver.go
package vfs // import "github.com/docker/docker/daemon/graphdriver/vfs"
import (
"fmt"
"os"
"path/filepath"
"github.com/docker/docker/daemon/graphdriver"
"github.com/docker/docker/errdefs"
"github.com/docker/docker/internal/containerfs"
"github.com/docker/docker/pkg/idtools"
"github.com/docker/docker/pkg/parsers"
"github.com/docker/docker/quota"
units "github.com/docker/go-units"
"github.com/opencontainers/selinux/go-selinux/label"
"github.com/pkg/errors"
)
const (
xattrsStorageOpt = "vfs.xattrs"
bestEffortXattrsOptValue = "i_want_broken_containers"
)
// CopyDir defines the copy method to use.
var 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 []string, idMap idtools.IdentityMapping) (graphdriver.Driver, error) {
d := &Driver{
home: home,
idMapping: idMap,
}
if err := d.parseOptions(options); err != nil {
return nil, err
}
dirID := idtools.Identity{
UID: idtools.CurrentIdentity().UID,
GID: d.idMapping.RootPair().GID,
}
if err := idtools.MkdirAllAndChown(home, 0o710, dirID); err != nil {
return nil, err
}
setupDriverQuota(d)
if size := d.getQuotaOpt(); !d.quotaSupported() && size > 0 {
return nil, quota.ErrQuotaNotSupported
}
return &graphdriver.NaiveDiffDriver{
ProtoDriver: d,
IDMap: d.idMapping,
BestEffortXattrs: d.bestEffortXattrs,
}, 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 {
driverQuota
home string
idMapping idtools.IdentityMapping
bestEffortXattrs bool
}
func (d *Driver) String() string {
return "vfs"
}
// Status is used for implementing the graphdriver.ProtoDriver interface.
func (d *Driver) Status() [][2]string {
if d.bestEffortXattrs {
return [][2]string{
// These strings are looked for in daemon/info_unix.go:fillDriverWarnings()
// because plumbing is hard and temporary is forever. Forgive me.
{"Extended file attributes", "best-effort"},
}
}
return nil
}
// GetMetadata is used for implementing the graphdriver.ProtoDriver interface. VFS does not currently have any meta data.
func (d *Driver) GetMetadata(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
}
func (d *Driver) parseOptions(options []string) error {
for _, option := range options {
key, val, err := parsers.ParseKeyValueOpt(option)
if err != nil {
return errdefs.InvalidParameter(err)
}
switch key {
case "size":
size, err := units.RAMInBytes(val)
if err != nil {
return errdefs.InvalidParameter(err)
}
if err = d.setQuotaOpt(uint64(size)); err != nil {
return errdefs.InvalidParameter(errors.Wrap(err, "failed to set option size for vfs"))
}
case xattrsStorageOpt:
if val != bestEffortXattrsOptValue {
return errdefs.InvalidParameter(errors.Errorf("do not set the " + xattrsStorageOpt + " option unless you are willing to accept the consequences"))
}
d.bestEffortXattrs = true
default:
return errdefs.InvalidParameter(errors.Errorf("unknown option %s for vfs", key))
}
}
return nil
}
// 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 {
quotaSize := d.getQuotaOpt()
if opts != nil {
for key, val := range opts.StorageOpt {
switch key {
case "size":
if !d.quotaSupported() {
return quota.ErrQuotaNotSupported
}
size, err := units.RAMInBytes(val)
if err != nil {
return errdefs.InvalidParameter(err)
}
quotaSize = uint64(size)
default:
return errdefs.InvalidParameter(errors.Errorf("Storage opt %s not supported", key))
}
}
}
return d.create(id, parent, quotaSize)
}
// 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 {
if opts != nil && len(opts.StorageOpt) != 0 {
return fmt.Errorf("--storage-opt is not supported for vfs on read-only layers")
}
return d.create(id, parent, 0)
}
func (d *Driver) create(id, parent string, size uint64) error {
dir := d.dir(id)
rootIDs := d.idMapping.RootPair()
dirID := idtools.Identity{
UID: idtools.CurrentIdentity().UID,
GID: rootIDs.GID,
}
if err := idtools.MkdirAllAndChown(filepath.Dir(dir), 0o710, dirID); err != nil {
return err
}
if err := idtools.MkdirAndChown(dir, 0o755, rootIDs); err != nil {
return err
}
if size != 0 {
if err := d.setupQuota(dir, size); err != nil {
return err
}
}
labelOpts := []string{"level:s0"}
if _, mountLabel, err := label.InitLabels(labelOpts); err == nil {
label.SetFileLabel(dir, mountLabel)
}
if parent == "" {
return nil
}
parentDir, err := d.Get(parent, "")
if err != nil {
return fmt.Errorf("%s: %s", parent, err)
}
return CopyDir(parentDir, dir)
}
func (d *Driver) dir(id string) string {
return filepath.Join(d.home, "dir", filepath.Base(id))
}
// Remove deletes the content from the directory for a given id.
func (d *Driver) Remove(id string) error {
return containerfs.EnsureRemoveAll(d.dir(id))
}
// Get returns the directory for the given id.
func (d *Driver) Get(id, mountLabel string) (string, error) {
dir := d.dir(id)
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
}