devmapper: Provide a function unregisterDevice()

Currently registerDevice() adds a device to in-memory table, saves metadata
and also updates the pool transaction ID.

Now move transaciton Id update out of registerDevice() and provide a new
function unregisterDevice() which does the reverse of registerDevice().
This will simplify some code down the line and make it more structured.

This is just code reorganization and should not change functionality.
 
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

daemon/graphdriver/devmapper/deviceset.go

@@ -274,13 +274,32 @@ func (devices *DeviceSet) lookupDevice(hash string) (*DevInfo, error) {
 	return info, nil
 }
 
-func (devices *DeviceSet) registerDevice(id int, hash string, size uint64) (*DevInfo, error) {
+func (devices *DeviceSet) unregisterDevice(id int, hash string) error {
+	log.Debugf("unregisterDevice(%v, %v)", id, hash)
+	info := &DevInfo{
+		Hash:     hash,
+		DeviceId: id,
+	}
+
+	devices.devicesLock.Lock()
+	delete(devices.Devices, hash)
+	devices.devicesLock.Unlock()
+
+	if err := devices.removeMetadata(info); err != nil {
+		log.Debugf("Error removing meta data: %s", err)
+		return err
+	}
+
+	return nil
+}
+
+func (devices *DeviceSet) registerDevice(id int, hash string, size uint64, transactionId uint64) (*DevInfo, error) {
 	log.Debugf("registerDevice(%v, %v)", id, hash)
 	info := &DevInfo{
 		Hash:          hash,
 		DeviceId:      id,
 		Size:          size,
-		TransactionId: devices.allocateTransactionId(),
+		TransactionId: transactionId,
 		Initialized:   false,
 		devices:       devices,
 	}
@@ -297,15 +316,6 @@ func (devices *DeviceSet) registerDevice(id int, hash string, size uint64) (*Dev
 		return nil, err
 	}
 
-	if err := devices.updatePoolTransactionId(); err != nil {
-		// Remove unused device
-		devices.devicesLock.Lock()
-		delete(devices.Devices, hash)
-		devices.devicesLock.Unlock()
-		devices.removeMetadata(info)
-		return nil, err
-	}
-
 	return info, nil
 }
 
@@ -489,13 +499,20 @@ func (devices *DeviceSet) setupBaseImage() error {
 		return err
 	}
 
+	transactionId := devices.allocateTransactionId()
 	log.Debugf("Registering base device (id %v) with FS size %v", deviceId, devices.baseFsSize)
-	info, err := devices.registerDevice(deviceId, "", devices.baseFsSize)
+	info, err := devices.registerDevice(deviceId, "", devices.baseFsSize, transactionId)
 	if err != nil {
 		_ = devicemapper.DeleteDevice(devices.getPoolDevName(), deviceId)
 		return err
 	}
 
+	if err := devices.updatePoolTransactionId(); err != nil {
+		devices.unregisterDevice(deviceId, "")
+		devicemapper.DeleteDevice(devices.getPoolDevName(), deviceId)
+		return err
+	}
+
 	log.Debugf("Creating filesystem on base device-mapper thin volume")
 
 	if err = devices.activateDeviceIfNeeded(info); err != nil {
@@ -815,11 +832,18 @@ func (devices *DeviceSet) AddDevice(hash, baseHash string) error {
 		return err
 	}
 
-	if _, err := devices.registerDevice(deviceId, hash, baseInfo.Size); err != nil {
+	transactionId := devices.allocateTransactionId()
+	if _, err := devices.registerDevice(deviceId, hash, baseInfo.Size, transactionId); err != nil {
 		devicemapper.DeleteDevice(devices.getPoolDevName(), deviceId)
 		log.Debugf("Error registering device: %s", err)
 		return err
 	}
+
+	if err := devices.updatePoolTransactionId(); err != nil {
+		devices.unregisterDevice(deviceId, hash)
+		devicemapper.DeleteDevice(devices.getPoolDevName(), deviceId)
+		return err
+	}
 	return nil
 }
 
@@ -848,12 +872,7 @@ func (devices *DeviceSet) deleteDevice(info *DevInfo) error {
 		return err
 	}
 
-	devices.devicesLock.Lock()
-	delete(devices.Devices, info.Hash)
-	devices.devicesLock.Unlock()
-
-	if err := devices.removeMetadata(info); err != nil {
-		log.Debugf("Error removing meta data: %s", err)
+	if err := devices.unregisterDevice(info.DeviceId, info.Hash); err != nil {
 		return err
 	}