fix in-kernel configuration serialization

this is uncritical, as we still also serialize in userland,
but to correctly serialize on the CONFIG_PENDING bit,
it must be wait_event(state_wait, \!test_and_set_bit)

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_nl.c

@@ -733,7 +733,7 @@ void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int max_seg_s) __mu
  */
 static void drbd_reconfig_start(struct drbd_conf *mdev)
 {
-	wait_event(mdev->state_wait, test_and_set_bit(CONFIG_PENDING, &mdev->flags));
+	wait_event(mdev->state_wait, !test_and_set_bit(CONFIG_PENDING, &mdev->flags));
 	wait_event(mdev->state_wait, !test_bit(DEVICE_DYING, &mdev->flags));
 	drbd_thread_start(&mdev->worker);
 }