workqueue: deprecate system_nrt[_freezable]_wq

system_nrt[_freezable]_wq are now spurious.  Mark them deprecated and
convert all users to system[_freezable]_wq.

If you're cc'd and wondering what's going on: Now all workqueues are
non-reentrant, so there's no reason to use system_nrt[_freezable]_wq.
Please use system[_freezable]_wq instead.

This patch doesn't make any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-By: Lai Jiangshan <laijs@cn.fujitsu.com>

Cc: Jens Axboe <axboe@kernel.dk>
Cc: David Airlie <airlied@linux.ie>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index e287c19..5a58e77 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -180,7 +180,7 @@
 
 /*
  * Worker for allocating per cpu stat for tgs. This is scheduled on the
- * system_nrt_wq once there are some groups on the alloc_list waiting for
+ * system_wq once there are some groups on the alloc_list waiting for
  * allocation.
  */
 static void tg_stats_alloc_fn(struct work_struct *work)
@@ -194,8 +194,7 @@
 		stats_cpu = alloc_percpu(struct tg_stats_cpu);
 		if (!stats_cpu) {
 			/* allocation failed, try again after some time */
-			queue_delayed_work(system_nrt_wq, dwork,
-					   msecs_to_jiffies(10));
+			schedule_delayed_work(dwork, msecs_to_jiffies(10));
 			return;
 		}
 	}
@@ -238,7 +237,7 @@
 	 */
 	spin_lock_irqsave(&tg_stats_alloc_lock, flags);
 	list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
-	queue_delayed_work(system_nrt_wq, &tg_stats_alloc_work, 0);
+	schedule_delayed_work(&tg_stats_alloc_work, 0);
 	spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
 }