drbd: use generic io stats accounting functions to simplify io stat accounting

Use generic io stats accounting help functions (generic_{start,end}_io_acct)
to simplify io stat accounting.
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/block/drbd/drbd_req.c

@@ -36,29 +36,15 @@ static bool drbd_may_do_local_read(struct drbd_device *device, sector_t sector,
 /* Update disk stats at start of I/O request */
 static void _drbd_start_io_acct(struct drbd_device *device, struct drbd_request *req)
 {
-	const int rw = bio_data_dir(req->master_bio);
-	int cpu;
-	cpu = part_stat_lock();
-	part_round_stats(cpu, &device->vdisk->part0);
-	part_stat_inc(cpu, &device->vdisk->part0, ios[rw]);
-	part_stat_add(cpu, &device->vdisk->part0, sectors[rw], req->i.size >> 9);
-	(void) cpu; /* The macro invocations above want the cpu argument, I do not like
-		       the compiler warning about cpu only assigned but never used... */
-	part_inc_in_flight(&device->vdisk->part0, rw);
-	part_stat_unlock();
+	generic_start_io_acct(bio_data_dir(req->master_bio), req->i.size >> 9,
+			      &device->vdisk->part0);
 }
 
 /* Update disk stats when completing request upwards */
 static void _drbd_end_io_acct(struct drbd_device *device, struct drbd_request *req)
 {
-	int rw = bio_data_dir(req->master_bio);
-	unsigned long duration = jiffies - req->start_jif;
-	int cpu;
-	cpu = part_stat_lock();
-	part_stat_add(cpu, &device->vdisk->part0, ticks[rw], duration);
-	part_round_stats(cpu, &device->vdisk->part0);
-	part_dec_in_flight(&device->vdisk->part0, rw);
-	part_stat_unlock();
+	generic_end_io_acct(bio_data_dir(req->master_bio),
+			    &device->vdisk->part0, req->start_jif);
 }
 
 static struct drbd_request *drbd_req_new(struct drbd_device *device,