block/bfq: Enable I/O statistics

BFQ uses io_start_time_ns. That member variable is only set if I/O
statistics are enabled. Hence this patch that enables I/O statistics
at the time BFQ is associated with a request queue.

Compile-tested only.

Reported-by: Cixi Geng <[email protected]>
Cc: Cixi Geng <[email protected]>
Cc: Yu Kuai <[email protected]>
Cc: Paolo Valente <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Bart Van Assche <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: bvanassche

block/bfq-iosched.c

@@ -7046,6 +7046,7 @@ static void bfq_exit_queue(struct elevator_queue *e)
 	spin_unlock_irq(&bfqd->lock);
 #endif
 
+	blk_stat_disable_accounting(bfqd->queue);
 	wbt_enable_default(bfqd->queue);
 
 	kfree(bfqd);
@@ -7192,6 +7193,8 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
 	blk_queue_flag_set(QUEUE_FLAG_SQ_SCHED, q);
 
 	wbt_disable_default(q);
+	blk_stat_enable_accounting(q);
+
 	return 0;
 
 out_free: