devmapper: Remove transaction Id update from saveMetaData()

Right now saveMetaData() is kind of little overloaded function. It is
supposed to save file metadata to disk. But in addition if user has
bumped up NewTransactionId before calling saveMetaData(), then it will
also update the transaction ID in pool.

Keep saveMetaData() simple and let it just save the file. Any update
of pool transaction ID is done inline in the code which needs it.

Also create an helper function updatePoolTransactionId() to update pool
transaction Id.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

daemon/graphdriver/devmapper/deviceset.go

@@ -204,6 +204,16 @@ func (devices *DeviceSet) allocateTransactionId() uint64 {
 	return devices.NewTransactionId
 }
 
+func (devices *DeviceSet) updatePoolTransactionId() error {
+	if devices.NewTransactionId != devices.TransactionId {
+		if err := devicemapper.SetTransactionId(devices.getPoolDevName(), devices.TransactionId, devices.NewTransactionId); err != nil {
+			return fmt.Errorf("Error setting devmapper transaction ID: %s", err)
+		}
+		devices.TransactionId = devices.NewTransactionId
+	}
+	return nil
+}
+
 func (devices *DeviceSet) removeMetadata(info *DevInfo) error {
 	if err := os.RemoveAll(devices.metadataFile(info)); err != nil {
 		return fmt.Errorf("Error removing metadata file %s: %s", devices.metadataFile(info), err)
@@ -246,13 +256,6 @@ func (devices *DeviceSet) saveMetadata(info *DevInfo) error {
 	if err := devices.writeMetaFile(jsonData, devices.metadataFile(info)); err != nil {
 		return err
 	}
-
-	if devices.NewTransactionId != devices.TransactionId {
-		if err = devicemapper.SetTransactionId(devices.getPoolDevName(), devices.TransactionId, devices.NewTransactionId); err != nil {
-			return fmt.Errorf("Error setting devmapper transition ID: %s", err)
-		}
-		devices.TransactionId = devices.NewTransactionId
-	}
 	return nil
 }
 
@@ -294,6 +297,15 @@ 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
 }