[PATCH 2/3] nvme: improve the quiesce time for non blocking transports

[Chao Leng]

When work with nvme multipathing, if one path failed, the requests will
be canceled and retry on another path. Before cancel the requests,
nvme_stop_queues quiesce queues for all namespaces, now quiesce one by
one, if there is a large set of namespaces, it will take long time.
Because every synchronize_rcu may need more than 10 milliseconds,
the total waiting time will be long.
Quiesce all queues in parallel, and it is safe to synchronize_rcu once.
The quiesce time and I/O fail over time can be reduced to one
synchronize_rcu time.

Signed-off-by: Chao Leng <lengchao at huawei.com>
---
 drivers/nvme/host/core.c | 34 ++++++++++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index eabffbc708cd..fcfa27e1078a 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4924,6 +4924,30 @@ static void nvme_stop_ns_queue(struct nvme_ns *ns)
 		blk_mq_wait_quiesce_done(ns->queue);
 }
 
+static void nvme_stop_ns_queue_nosync(struct nvme_ns *ns)
+{
+	if (!test_and_set_bit(NVME_NS_STOPPED, &ns->flags))
+		blk_mq_quiesce_queue_nowait(ns->queue);
+}
+
+static void nvme_stop_blocking_queues(struct nvme_ctrl *ctrl)
+{
+	struct nvme_ns *ns;
+
+	list_for_each_entry(ns, &ctrl->namespaces, list)
+		nvme_stop_ns_queue(ns);
+}
+
+static void nvme_stop_nonblocking_queues(struct nvme_ctrl *ctrl)
+{
+	struct nvme_ns *ns;
+
+	list_for_each_entry(ns, &ctrl->namespaces, list)
+		nvme_stop_ns_queue_nosync(ns);
+
+	synchronize_rcu();
+}
+
 /*
  * Prepare a queue for teardown.
  *
@@ -5017,11 +5041,13 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
 
 void nvme_stop_queues(struct nvme_ctrl *ctrl)
 {
-	struct nvme_ns *ns;
-
 	down_read(&ctrl->namespaces_rwsem);
-	list_for_each_entry(ns, &ctrl->namespaces, list)
-		nvme_stop_ns_queue(ns);
+
+	if (ctrl->tagset->flags & BLK_MQ_F_BLOCKING)
+		nvme_stop_blocking_queues(ctrl);
+	else
+		nvme_stop_nonblocking_queues(ctrl);
+
 	up_read(&ctrl->namespaces_rwsem);
 }
 EXPORT_SYMBOL_GPL(nvme_stop_queues);
-- 
2.16.4