docker-docs/daemon/graphdriver/devmapper/driver.go

// +build linux

package devmapper

import (
	"fmt"
	"io/ioutil"
	"os"
	"path"
	"strconv"

	"github.com/Sirupsen/logrus"

	"github.com/docker/docker/daemon/graphdriver"
	"github.com/docker/docker/pkg/devicemapper"
	"github.com/docker/docker/pkg/idtools"
	"github.com/docker/docker/pkg/mount"
	"github.com/docker/docker/pkg/units"
)

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

// Placeholder interfaces, to be replaced
// at integration.

// End of placeholder interfaces.

// Driver contains the device set mounted and the home directory
type Driver struct {
	*DeviceSet
	home    string
	uidMaps []idtools.IDMap
	gidMaps []idtools.IDMap
}

var backingFs = "<unknown>"

// Init creates a driver with the given home and the set of options.
func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (graphdriver.Driver, error) {
	fsMagic, err := graphdriver.GetFSMagic(home)
	if err != nil {
		return nil, err
	}
	if fsName, ok := graphdriver.FsNames[fsMagic]; ok {
		backingFs = fsName
	}

	deviceSet, err := NewDeviceSet(home, true, options, uidMaps, gidMaps)
	if err != nil {
		return nil, err
	}

	if err := mount.MakePrivate(home); err != nil {
		return nil, err
	}

	d := &Driver{
		DeviceSet: deviceSet,
		home:      home,
		uidMaps:   uidMaps,
		gidMaps:   gidMaps,
	}

	return graphdriver.NewNaiveDiffDriver(d, uidMaps, gidMaps), nil
}

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

// Status returns the status about the driver in a printable format.
// Information returned contains Pool Name, Data File, Metadata file, disk usage by
// the data and metadata, etc.
func (d *Driver) Status() [][2]string {
	s := d.DeviceSet.Status()

	status := [][2]string{
		{"Pool Name", s.PoolName},
		{"Pool Blocksize", fmt.Sprintf("%s", units.HumanSize(float64(s.SectorSize)))},
		{"Base Device Size", fmt.Sprintf("%s", units.HumanSize(float64(s.BaseDeviceSize)))},
		{"Backing Filesystem", backingFs},
		{"Data file", s.DataFile},
		{"Metadata file", s.MetadataFile},
		{"Data Space Used", fmt.Sprintf("%s", units.HumanSize(float64(s.Data.Used)))},
		{"Data Space Total", fmt.Sprintf("%s", units.HumanSize(float64(s.Data.Total)))},
		{"Data Space Available", fmt.Sprintf("%s", units.HumanSize(float64(s.Data.Available)))},
		{"Metadata Space Used", fmt.Sprintf("%s", units.HumanSize(float64(s.Metadata.Used)))},
		{"Metadata Space Total", fmt.Sprintf("%s", units.HumanSize(float64(s.Metadata.Total)))},
		{"Metadata Space Available", fmt.Sprintf("%s", units.HumanSize(float64(s.Metadata.Available)))},
		{"Udev Sync Supported", fmt.Sprintf("%v", s.UdevSyncSupported)},
		{"Deferred Removal Enabled", fmt.Sprintf("%v", s.DeferredRemoveEnabled)},
		{"Deferred Deletion Enabled", fmt.Sprintf("%v", s.DeferredDeleteEnabled)},
		{"Deferred Deleted Device Count", fmt.Sprintf("%v", s.DeferredDeletedDeviceCount)},
	}
	if len(s.DataLoopback) > 0 {
		status = append(status, [2]string{"Data loop file", s.DataLoopback})
	}
	if len(s.MetadataLoopback) > 0 {
		status = append(status, [2]string{"Metadata loop file", s.MetadataLoopback})
	}
	if vStr, err := devicemapper.GetLibraryVersion(); err == nil {
		status = append(status, [2]string{"Library Version", vStr})
	}
	return status
}

// GetMetadata returns a map of information about the device.
func (d *Driver) GetMetadata(id string) (map[string]string, error) {
	m, err := d.DeviceSet.exportDeviceMetadata(id)

	if err != nil {
		return nil, err
	}

	metadata := make(map[string]string)
	metadata["DeviceId"] = strconv.Itoa(m.deviceID)
	metadata["DeviceSize"] = strconv.FormatUint(m.deviceSize, 10)
	metadata["DeviceName"] = m.deviceName
	return metadata, nil
}

// Cleanup unmounts a device.
func (d *Driver) Cleanup() error {
	err := d.DeviceSet.Shutdown()

	if err2 := mount.Unmount(d.home); err == nil {
		err = err2
	}

	return err
}

// Create adds a device with a given id and the parent.
func (d *Driver) Create(id, parent, mountLabel string) error {
	if err := d.DeviceSet.AddDevice(id, parent); err != nil {
		return err
	}

	return nil
}

// Remove removes a device with a given id, unmounts the filesystem.
func (d *Driver) Remove(id string) error {
	if !d.DeviceSet.HasDevice(id) {
		// Consider removing a non-existing device a no-op
		// This is useful to be able to progress on container removal
		// if the underlying device has gone away due to earlier errors
		return nil
	}

	// This assumes the device has been properly Get/Put:ed and thus is unmounted
	if err := d.DeviceSet.DeleteDevice(id, false); err != nil {
		return err
	}

	mp := path.Join(d.home, "mnt", id)
	if err := os.RemoveAll(mp); err != nil && !os.IsNotExist(err) {
		return err
	}

	return nil
}

// Get mounts a device with given id into the root filesystem
func (d *Driver) Get(id, mountLabel string) (string, error) {
	mp := path.Join(d.home, "mnt", id)

	uid, gid, err := idtools.GetRootUIDGID(d.uidMaps, d.gidMaps)
	if err != nil {
		return "", err
	}
	// Create the target directories if they don't exist
	if err := idtools.MkdirAllAs(path.Join(d.home, "mnt"), 0755, uid, gid); err != nil && !os.IsExist(err) {
		return "", err
	}
	if err := idtools.MkdirAs(mp, 0755, uid, gid); err != nil && !os.IsExist(err) {
		return "", err
	}

	// Mount the device
	if err := d.DeviceSet.MountDevice(id, mp, mountLabel); err != nil {
		return "", err
	}

	rootFs := path.Join(mp, "rootfs")
	if err := idtools.MkdirAllAs(rootFs, 0755, uid, gid); err != nil && !os.IsExist(err) {
		d.DeviceSet.UnmountDevice(id)
		return "", err
	}

	idFile := path.Join(mp, "id")
	if _, err := os.Stat(idFile); err != nil && os.IsNotExist(err) {
		// Create an "id" file with the container/image id in it to help reconscruct this in case
		// of later problems
		if err := ioutil.WriteFile(idFile, []byte(id), 0600); err != nil {
			d.DeviceSet.UnmountDevice(id)
			return "", err
		}
	}

	return rootFs, nil
}

// Put unmounts a device and removes it.
func (d *Driver) Put(id string) error {
	err := d.DeviceSet.UnmountDevice(id)
	if err != nil {
		logrus.Errorf("Error unmounting device %s: %s", id, err)
	}
	return err
}

// Exists checks to see if the device exists.
func (d *Driver) Exists(id string) bool {
	return d.DeviceSet.HasDevice(id)
}