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moby--moby/daemon/graphdriver/vfs/driver.go
Stefan J. Wernli ef5bfad321 Adding readOnly parameter to graphdriver Create method
Since the layer store was introduced, the level above the graphdriver
now differentiates between read/write and read-only layers.  This
distinction is useful for graphdrivers that need to take special steps
when creating a layer based on whether it is read-only or not.
Adding this parameter allows the graphdrivers to differentiate, which
in the case of the Windows graphdriver, removes our dependence on parsing
the id of the parent for "-init" in order to infer this information.

This will also set the stage for unblocking some of the layer store
unit tests in the next preview build of Windows.

Signed-off-by: Stefan J. Wernli <swernli@microsoft.com>
2016-04-06 13:52:53 -07:00

145 lines
4.1 KiB
Go

package vfs
import (
"fmt"
"os"
"path/filepath"
"github.com/docker/docker/daemon/graphdriver"
"github.com/docker/docker/pkg/chrootarchive"
"github.com/docker/docker/pkg/idtools"
"github.com/opencontainers/runc/libcontainer/label"
)
var (
// CopyWithTar defines the copy method to use.
CopyWithTar = chrootarchive.CopyWithTar
)
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, uidMaps, gidMaps []idtools.IDMap) (graphdriver.Driver, error) {
d := &Driver{
home: home,
uidMaps: uidMaps,
gidMaps: gidMaps,
}
rootUID, rootGID, err := idtools.GetRootUIDGID(uidMaps, gidMaps)
if err != nil {
return nil, err
}
if err := idtools.MkdirAllAs(home, 0700, rootUID, rootGID); err != nil {
return nil, err
}
return graphdriver.NewNaiveDiffDriver(d, uidMaps, gidMaps), 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 {
home string
uidMaps []idtools.IDMap
gidMaps []idtools.IDMap
}
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
}
// 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
}
// CreateReadWrite creates a layer that is writable for use as a container
// file system.
func (d *Driver) CreateReadWrite(id, parent, mountLabel string, storageOpt map[string]string) error {
return d.Create(id, parent, mountLabel, storageOpt)
}
// 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, mountLabel string, storageOpt map[string]string) error {
if len(storageOpt) != 0 {
return fmt.Errorf("--storage-opt is not supported for vfs")
}
dir := d.dir(id)
rootUID, rootGID, err := idtools.GetRootUIDGID(d.uidMaps, d.gidMaps)
if err != nil {
return err
}
if err := idtools.MkdirAllAs(filepath.Dir(dir), 0700, rootUID, rootGID); err != nil {
return err
}
if err := idtools.MkdirAs(dir, 0755, rootUID, rootGID); err != nil {
return err
}
opts := []string{"level:s0"}
if _, mountLabel, err := label.InitLabels(opts); 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)
}
if err := CopyWithTar(parentDir, dir); err != nil {
return err
}
return nil
}
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 {
if err := os.RemoveAll(d.dir(id)); err != nil && !os.IsNotExist(err) {
return err
}
return nil
}
// 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
}