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moby--moby/volume/local/local.go
Brian Goff db3576f8a0 Ensure unmount before removing local volume.
When there is an error unmounting a local volume, it is still possible
to call `Remove()` on the volume causing removal of the mounted
resources which is generally not desirable.

This ensures that resources are unmounted before attempting removal.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
2017-04-27 16:41:03 -04:00

389 lines
9.7 KiB
Go

// Package local provides the default implementation for volumes. It
// is used to mount data volume containers and directories local to
// the host server.
package local
import (
"encoding/json"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"reflect"
"strings"
"sync"
"github.com/pkg/errors"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/api"
"github.com/docker/docker/pkg/idtools"
"github.com/docker/docker/pkg/mount"
"github.com/docker/docker/volume"
)
// VolumeDataPathName is the name of the directory where the volume data is stored.
// It uses a very distinctive name to avoid collisions migrating data between
// Docker versions.
const (
VolumeDataPathName = "_data"
volumesPathName = "volumes"
)
var (
// ErrNotFound is the typed error returned when the requested volume name can't be found
ErrNotFound = fmt.Errorf("volume not found")
// volumeNameRegex ensures the name assigned for the volume is valid.
// This name is used to create the bind directory, so we need to avoid characters that
// would make the path to escape the root directory.
volumeNameRegex = api.RestrictedNamePattern
)
type validationError struct {
error
}
func (validationError) IsValidationError() bool {
return true
}
type activeMount struct {
count uint64
mounted bool
}
// New instantiates a new Root instance with the provided scope. Scope
// is the base path that the Root instance uses to store its
// volumes. The base path is created here if it does not exist.
func New(scope string, rootUID, rootGID int) (*Root, error) {
rootDirectory := filepath.Join(scope, volumesPathName)
if err := idtools.MkdirAllAs(rootDirectory, 0700, rootUID, rootGID); err != nil {
return nil, err
}
r := &Root{
scope: scope,
path: rootDirectory,
volumes: make(map[string]*localVolume),
rootUID: rootUID,
rootGID: rootGID,
}
dirs, err := ioutil.ReadDir(rootDirectory)
if err != nil {
return nil, err
}
mountInfos, err := mount.GetMounts()
if err != nil {
logrus.Debugf("error looking up mounts for local volume cleanup: %v", err)
}
for _, d := range dirs {
if !d.IsDir() {
continue
}
name := filepath.Base(d.Name())
v := &localVolume{
driverName: r.Name(),
name: name,
path: r.DataPath(name),
}
r.volumes[name] = v
optsFilePath := filepath.Join(rootDirectory, name, "opts.json")
if b, err := ioutil.ReadFile(optsFilePath); err == nil {
opts := optsConfig{}
if err := json.Unmarshal(b, &opts); err != nil {
return nil, errors.Wrapf(err, "error while unmarshaling volume options for volume: %s", name)
}
// Make sure this isn't an empty optsConfig.
// This could be empty due to buggy behavior in older versions of Docker.
if !reflect.DeepEqual(opts, optsConfig{}) {
v.opts = &opts
}
// unmount anything that may still be mounted (for example, from an unclean shutdown)
for _, info := range mountInfos {
if info.Mountpoint == v.path {
mount.Unmount(v.path)
break
}
}
}
}
return r, nil
}
// Root implements the Driver interface for the volume package and
// manages the creation/removal of volumes. It uses only standard vfs
// commands to create/remove dirs within its provided scope.
type Root struct {
m sync.Mutex
scope string
path string
volumes map[string]*localVolume
rootUID int
rootGID int
}
// List lists all the volumes
func (r *Root) List() ([]volume.Volume, error) {
var ls []volume.Volume
r.m.Lock()
for _, v := range r.volumes {
ls = append(ls, v)
}
r.m.Unlock()
return ls, nil
}
// DataPath returns the constructed path of this volume.
func (r *Root) DataPath(volumeName string) string {
return filepath.Join(r.path, volumeName, VolumeDataPathName)
}
// Name returns the name of Root, defined in the volume package in the DefaultDriverName constant.
func (r *Root) Name() string {
return volume.DefaultDriverName
}
// Create creates a new volume.Volume with the provided name, creating
// the underlying directory tree required for this volume in the
// process.
func (r *Root) Create(name string, opts map[string]string) (volume.Volume, error) {
if err := r.validateName(name); err != nil {
return nil, err
}
r.m.Lock()
defer r.m.Unlock()
v, exists := r.volumes[name]
if exists {
return v, nil
}
path := r.DataPath(name)
if err := idtools.MkdirAllAs(path, 0755, r.rootUID, r.rootGID); err != nil {
if os.IsExist(err) {
return nil, fmt.Errorf("volume already exists under %s", filepath.Dir(path))
}
return nil, errors.Wrapf(err, "error while creating volume path '%s'", path)
}
var err error
defer func() {
if err != nil {
os.RemoveAll(filepath.Dir(path))
}
}()
v = &localVolume{
driverName: r.Name(),
name: name,
path: path,
}
if len(opts) != 0 {
if err = setOpts(v, opts); err != nil {
return nil, err
}
var b []byte
b, err = json.Marshal(v.opts)
if err != nil {
return nil, err
}
if err = ioutil.WriteFile(filepath.Join(filepath.Dir(path), "opts.json"), b, 600); err != nil {
return nil, errors.Wrap(err, "error while persisting volume options")
}
}
r.volumes[name] = v
return v, nil
}
// Remove removes the specified volume and all underlying data. If the
// given volume does not belong to this driver and an error is
// returned. The volume is reference counted, if all references are
// not released then the volume is not removed.
func (r *Root) Remove(v volume.Volume) error {
r.m.Lock()
defer r.m.Unlock()
lv, ok := v.(*localVolume)
if !ok {
return fmt.Errorf("unknown volume type %T", v)
}
if lv.active.count > 0 {
return fmt.Errorf("volume has active mounts")
}
if err := lv.unmount(); err != nil {
return err
}
realPath, err := filepath.EvalSymlinks(lv.path)
if err != nil {
if !os.IsNotExist(err) {
return err
}
realPath = filepath.Dir(lv.path)
}
if !r.scopedPath(realPath) {
return fmt.Errorf("Unable to remove a directory of out the Docker root %s: %s", r.scope, realPath)
}
if err := removePath(realPath); err != nil {
return err
}
delete(r.volumes, lv.name)
return removePath(filepath.Dir(lv.path))
}
func removePath(path string) error {
if err := os.RemoveAll(path); err != nil {
if os.IsNotExist(err) {
return nil
}
return errors.Wrapf(err, "error removing volume path '%s'", path)
}
return nil
}
// Get looks up the volume for the given name and returns it if found
func (r *Root) Get(name string) (volume.Volume, error) {
r.m.Lock()
v, exists := r.volumes[name]
r.m.Unlock()
if !exists {
return nil, ErrNotFound
}
return v, nil
}
// Scope returns the local volume scope
func (r *Root) Scope() string {
return volume.LocalScope
}
func (r *Root) validateName(name string) error {
if len(name) == 1 {
return validationError{fmt.Errorf("volume name is too short, names should be at least two alphanumeric characters")}
}
if !volumeNameRegex.MatchString(name) {
return validationError{fmt.Errorf("%q includes invalid characters for a local volume name, only %q are allowed. If you intended to pass a host directory, use absolute path", name, api.RestrictedNameChars)}
}
return nil
}
// localVolume implements the Volume interface from the volume package and
// represents the volumes created by Root.
type localVolume struct {
m sync.Mutex
// unique name of the volume
name string
// path is the path on the host where the data lives
path string
// driverName is the name of the driver that created the volume.
driverName string
// opts is the parsed list of options used to create the volume
opts *optsConfig
// active refcounts the active mounts
active activeMount
}
// Name returns the name of the given Volume.
func (v *localVolume) Name() string {
return v.name
}
// DriverName returns the driver that created the given Volume.
func (v *localVolume) DriverName() string {
return v.driverName
}
// Path returns the data location.
func (v *localVolume) Path() string {
return v.path
}
// Mount implements the localVolume interface, returning the data location.
// If there are any provided mount options, the resources will be mounted at this point
func (v *localVolume) Mount(id string) (string, error) {
v.m.Lock()
defer v.m.Unlock()
if v.opts != nil {
if !v.active.mounted {
if err := v.mount(); err != nil {
return "", err
}
v.active.mounted = true
}
v.active.count++
}
return v.path, nil
}
// Unmount dereferences the id, and if it is the last reference will unmount any resources
// that were previously mounted.
func (v *localVolume) Unmount(id string) error {
v.m.Lock()
defer v.m.Unlock()
// Always decrement the count, even if the unmount fails
// Essentially docker doesn't care if this fails, it will send an error, but
// ultimately there's nothing that can be done. If we don't decrement the count
// this volume can never be removed until a daemon restart occurs.
if v.opts != nil {
v.active.count--
}
if v.active.count > 0 {
return nil
}
return v.unmount()
}
func (v *localVolume) unmount() error {
if v.opts != nil {
if err := mount.Unmount(v.path); err != nil {
if mounted, mErr := mount.Mounted(v.path); mounted || mErr != nil {
return errors.Wrapf(err, "error while unmounting volume path '%s'", v.path)
}
}
v.active.mounted = false
}
return nil
}
func validateOpts(opts map[string]string) error {
for opt := range opts {
if !validOpts[opt] {
return validationError{fmt.Errorf("invalid option key: %q", opt)}
}
}
return nil
}
func (v *localVolume) Status() map[string]interface{} {
return nil
}
// getAddress finds out address/hostname from options
func getAddress(opts string) string {
optsList := strings.Split(opts, ",")
for i := 0; i < len(optsList); i++ {
if strings.HasPrefix(optsList[i], "addr=") {
addr := (strings.SplitN(optsList[i], "=", 2)[1])
return addr
}
}
return ""
}