nvme: fix nvme_stop_queues cost long time error

driver inclusion
category: bugfix
bugzilla: NA
Link: https://gitee.com/openeuler/kernel/issues/I1WGZE

--------------------------------

It will cost a lot of time when synchronize_rcu() is called for every
namspace in nvme_stop_queues().
Reviewed-by: NChao Leng <lengchao@huawei.com>
Reviewed-by: NJike Cheng <chengjike.cheng@huawei.com>
Signed-off-by: NDi Wang <wangdi44@huawei.com>
Signed-off-by: NLijie <lijie34@huawei.com>
Acked-by: NHanjun Guo <guohanjun@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

block/blk-mq.c

@@ -242,6 +242,24 @@ void blk_mq_quiesce_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
 
+bool blk_mq_quiesce_queue_without_rcu(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned int i;
+	bool rcu = false;
+
+	blk_mq_quiesce_queue_nowait(q);
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (hctx->flags & BLK_MQ_F_BLOCKING)
+			synchronize_srcu(hctx->srcu);
+		else
+			rcu = true;
+	}
+	return rcu;
+}
+EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_without_rcu);
+
 /*
  * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
  * @q: request queue.

drivers/nvme/host/core.c

@@ -3904,11 +3904,15 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
 void nvme_stop_queues(struct nvme_ctrl *ctrl)
 {
 	struct nvme_ns *ns;
+	bool rcu = false;
 
 	down_read(&ctrl->namespaces_rwsem);
 	list_for_each_entry(ns, &ctrl->namespaces, list)
-		blk_mq_quiesce_queue(ns->queue);
+		rcu = (blk_mq_quiesce_queue_without_rcu(ns->queue) || rcu);
 	up_read(&ctrl->namespaces_rwsem);
+
+	if (rcu)
+		synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(nvme_stop_queues);
 

include/linux/blk-mq.h

@@ -309,6 +309,7 @@ void blk_mq_start_hw_queues(struct request_queue *q);
 void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async);
 void blk_mq_quiesce_queue(struct request_queue *q);
+bool blk_mq_quiesce_queue_without_rcu(struct request_queue *q);
 void blk_mq_unquiesce_queue(struct request_queue *q);
 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs);
 bool blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);