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driver.go
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driver.go
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// +build linux,amd64
package devmapper
import (
"fmt"
"github.com/dotcloud/docker/graphdriver"
"github.com/dotcloud/docker/utils"
"io/ioutil"
"path"
"sync"
)
func init() {
graphdriver.Register("devicemapper", Init)
}
// Placeholder interfaces, to be replaced
// at integration.
// End of placeholder interfaces.
type Driver struct {
*DeviceSet
home string
sync.Mutex // Protects concurrent modification to active
active map[string]int
}
var Init = func(home string) (graphdriver.Driver, error) {
deviceSet, err := NewDeviceSet(home, true)
if err != nil {
return nil, err
}
d := &Driver{
DeviceSet: deviceSet,
home: home,
active: make(map[string]int),
}
return d, nil
}
func (d *Driver) String() string {
return "devicemapper"
}
func (d *Driver) Status() [][2]string {
s := d.DeviceSet.Status()
status := [][2]string{
{"Pool Name", s.PoolName},
{"Data file", s.DataLoopback},
{"Metadata file", s.MetadataLoopback},
{"Data Space Used", fmt.Sprintf("%.1f Mb", float64(s.Data.Used)/(1024*1024))},
{"Data Space Total", fmt.Sprintf("%.1f Mb", float64(s.Data.Total)/(1024*1024))},
{"Metadata Space Used", fmt.Sprintf("%.1f Mb", float64(s.Metadata.Used)/(1024*1024))},
{"Metadata Space Total", fmt.Sprintf("%.1f Mb", float64(s.Metadata.Total)/(1024*1024))},
}
return status
}
func (d *Driver) Cleanup() error {
return d.DeviceSet.Shutdown()
}
func (d *Driver) Create(id, parent string) error {
if err := d.DeviceSet.AddDevice(id, parent); err != nil {
return err
}
mp := path.Join(d.home, "mnt", id)
if err := d.mount(id, mp); err != nil {
return err
}
if err := osMkdirAll(path.Join(mp, "rootfs"), 0755); err != nil && !osIsExist(err) {
return 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(path.Join(mp, "id"), []byte(id), 0600); err != nil {
return err
}
return nil
}
func (d *Driver) Remove(id string) error {
// Protect the d.active from concurrent access
d.Lock()
defer d.Unlock()
if d.active[id] != 0 {
utils.Errorf("Warning: removing active id %s\n", id)
}
mp := path.Join(d.home, "mnt", id)
if err := d.unmount(id, mp); err != nil {
return err
}
return d.DeviceSet.RemoveDevice(id)
}
func (d *Driver) Get(id string) (string, error) {
// Protect the d.active from concurrent access
d.Lock()
defer d.Unlock()
count := d.active[id]
mp := path.Join(d.home, "mnt", id)
if count == 0 {
if err := d.mount(id, mp); err != nil {
return "", err
}
}
d.active[id] = count + 1
return path.Join(mp, "rootfs"), nil
}
func (d *Driver) Put(id string) {
// Protect the d.active from concurrent access
d.Lock()
defer d.Unlock()
if count := d.active[id]; count > 1 {
d.active[id] = count - 1
} else {
mp := path.Join(d.home, "mnt", id)
d.unmount(id, mp)
delete(d.active, id)
}
}
func (d *Driver) mount(id, mountPoint string) error {
// Create the target directories if they don't exist
if err := osMkdirAll(mountPoint, 0755); err != nil && !osIsExist(err) {
return err
}
// If mountpoint is already mounted, do nothing
if mounted, err := Mounted(mountPoint); err != nil {
return fmt.Errorf("Error checking mountpoint: %s", err)
} else if mounted {
return nil
}
// Mount the device
return d.DeviceSet.MountDevice(id, mountPoint, false)
}
func (d *Driver) unmount(id, mountPoint string) error {
// If mountpoint is not mounted, do nothing
if mounted, err := Mounted(mountPoint); err != nil {
return fmt.Errorf("Error checking mountpoint: %s", err)
} else if !mounted {
return nil
}
// Unmount the device
return d.DeviceSet.UnmountDevice(id, mountPoint, true)
}
func (d *Driver) Exists(id string) bool {
return d.Devices[id] != nil
}