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devicemapper: Don't mount in Create() 

We used to mount in Create() to be able to create a few files that
needs to be in each device. However, this mount is problematic for
selinux, as we need to set the mount label at mount-time, and it
is not known at the time of Create().

This change just moves the file creation to first Get() call and
drops the mount from Create(). Additionally, this lets us remove
some complexities we had to avoid an extra unmount+mount cycle.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
This commit is contained in:
Alexander Larsson 2014-04-23 13:50:53 +02:00
parent f436c744da
commit 73d9ede12c
3 changed files with 30 additions and 89 deletions
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44
daemon/graphdriver/devmapper/deviceset.go
View File

@ -35,12 +35,6 @@ type DevInfo struct {
mountCount int `json:"-"`
mountPath string `json:"-"`
// A floating mount means one reference is not owned and
// will be stolen by the next mount. This allows us to
// avoid unmounting directly after creation before the
// first get (since we need to mount to set up the device
// a bit first).
floating bool `json:"-"`
// The global DeviceSet lock guarantees that we serialize all
// the calls to libdevmapper (which is not threadsafe), but we
@ -94,14 +88,6 @@ type DevStatus struct {
HighestMappedSector uint64
}
type UnmountMode int
const (
UnmountRegular UnmountMode = iota
UnmountFloat
UnmountSink
)
func getDevName(name string) string {
return "/dev/mapper/" + name
}
@ -876,12 +862,7 @@ func (devices *DeviceSet) MountDevice(hash, path string, mountLabel string) erro
return fmt.Errorf("Trying to mount devmapper device in multple places (%s, %s)", info.mountPath, path)
}
if info.floating {
// Steal floating ref
info.floating = false
} else {
info.mountCount++
}
info.mountCount++
return nil
}
@ -903,13 +884,12 @@ func (devices *DeviceSet) MountDevice(hash, path string, mountLabel string) erro
info.mountCount = 1
info.mountPath = path
info.floating = false
return devices.setInitialized(info)
}
func (devices *DeviceSet) UnmountDevice(hash string, mode UnmountMode) error {
utils.Debugf("[devmapper] UnmountDevice(hash=%s, mode=%d)", hash, mode)
func (devices *DeviceSet) UnmountDevice(hash string) error {
utils.Debugf("[devmapper] UnmountDevice(hash=%s)", hash)
defer utils.Debugf("[devmapper] UnmountDevice END")
info, err := devices.lookupDevice(hash)
@ -923,24 +903,6 @@ func (devices *DeviceSet) UnmountDevice(hash string, mode UnmountMode) error {
devices.Lock()
defer devices.Unlock()
if mode == UnmountFloat {
if info.floating {
return fmt.Errorf("UnmountDevice: can't float floating reference %s\n", hash)
}
// Leave this reference floating
info.floating = true
return nil
}
if mode == UnmountSink {
if !info.floating {
// Someone already sunk this
return nil
}
// Otherwise, treat this as a regular unmount
}
if info.mountCount == 0 {
return fmt.Errorf("UnmountDevice: device not-mounted id %s\n", hash)
}

64
daemon/graphdriver/devmapper/driver.go
View File

@ -64,26 +64,6 @@ func (d *Driver) Create(id, parent string, mountLabel 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
}
// We float this reference so that the next Get call can
// steal it, so we don't have to unmount
if err := d.DeviceSet.UnmountDevice(id, UnmountFloat); err != nil {
return err
}
return nil
}
@ -96,10 +76,6 @@ func (d *Driver) Remove(id string) error {
return nil
}
// Sink the float from create in case no Get() call was made
if err := d.DeviceSet.UnmountDevice(id, UnmountSink); err != nil {
return err
}
// This assumes the device has been properly Get/Put:ed and thus is unmounted
if err := d.DeviceSet.DeleteDevice(id); err != nil {
return err
@ -115,28 +91,42 @@ func (d *Driver) Remove(id string) error {
func (d *Driver) Get(id string) (string, error) {
mp := path.Join(d.home, "mnt", id)
if err := d.mount(id, mp); err != nil {
// Create the target directories if they don't exist
if err := osMkdirAll(mp, 0755); err != nil && !osIsExist(err) {
return "", err
}
return path.Join(mp, "rootfs"), nil
// Mount the device
if err := d.DeviceSet.MountDevice(id, mp, ""); err != nil {
return "", err
}
rootFs := path.Join(mp, "rootfs")
if err := osMkdirAll(rootFs, 0755); err != nil && !osIsExist(err) {
d.DeviceSet.UnmountDevice(id)
return "", err
}
idFile := path.Join(mp, "id")
if _, err := osStat(idFile); err != nil && osIsNotExist(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
}
func (d *Driver) Put(id string) {
if err := d.DeviceSet.UnmountDevice(id, UnmountRegular); err != nil {
if err := d.DeviceSet.UnmountDevice(id); err != nil {
utils.Errorf("Warning: error unmounting device %s: %s\n", id, err)
}
}
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
}
// Mount the device
return d.DeviceSet.MountDevice(id, mountPoint, "")
}
func (d *Driver) Exists(id string) bool {
return d.Devices[id] != nil
return d.DeviceSet.HasDevice(id)
}

11
daemon/graphdriver/devmapper/driver_test.go
View File

@ -500,15 +500,10 @@ func TestDriverCreate(t *testing.T) {
calls.Assert(t,
"DmTaskCreate",
"DmTaskGetInfo",
"sysMount",
"DmTaskRun",
"DmTaskSetTarget",
"DmTaskSetSector",
"DmTaskSetCookie",
"DmUdevWait",
"DmTaskSetName",
"DmTaskSetMessage",
"DmTaskSetAddNode",
)
}()
@ -619,15 +614,10 @@ func TestDriverRemove(t *testing.T) {
calls.Assert(t,
"DmTaskCreate",
"DmTaskGetInfo",
"sysMount",
"DmTaskRun",
"DmTaskSetTarget",
"DmTaskSetSector",
"DmTaskSetCookie",
"DmUdevWait",
"DmTaskSetName",
"DmTaskSetMessage",
"DmTaskSetAddNode",
)
Mounted = func(mnt string) (bool, error) {
@ -650,7 +640,6 @@ func TestDriverRemove(t *testing.T) {
"DmTaskSetTarget",
"DmTaskSetAddNode",
"DmUdevWait",
"sysUnmount",
)
}()
runtime.GC()