block,cfq: change code order

cfq_slice_expired will change saved_workload_slice. It should be called
first so saved_workload_slice is correctly set to 0 after workload type
is changed.
This fixes the code order changed by 54b466e4.
Tested-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/cfq-iosched.c

@@ -3117,17 +3117,18 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
  */
 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
+	enum wl_type_t old_type = cfqq_type(cfqd->active_queue);
+
 	cfq_log_cfqq(cfqd, cfqq, "preempt");
+	cfq_slice_expired(cfqd, 1);
 
 	/*
 	 * workload type is changed, don't save slice, otherwise preempt
 	 * doesn't happen
 	 */
-	if (cfqq_type(cfqd->active_queue) != cfqq_type(cfqq))
+	if (old_type != cfqq_type(cfqq))
 		cfqq->cfqg->saved_workload_slice = 0;
 
-	cfq_slice_expired(cfqd, 1);
-
 	/*
 	 * Put the new queue at the front of the of the current list,
 	 * so we know that it will be selected next.