[PATCH rfc 2/4] nvme: improve quiesce for blocking queues

[Sagi Grimberg]

nvme transports that use blocking hw queues (e.g. nvme-tcp) currently
will synchronize queue quiesce for each namespace at once. This can
slow down failover time (which first quiesce all ns queues) if we have
a large amount of namespaces. Instead, we want to use an async interface
and do the namespaces quiesce in parallel rather than serially.

Introduce nvme_stop_blocking_queues for transports that use blocking
hw queues and convert nvme-tcp to use the new interface.

Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
 drivers/nvme/host/core.c | 13 +++++++++++++
 drivers/nvme/host/nvme.h |  1 +
 drivers/nvme/host/tcp.c  |  1 +
 3 files changed, 15 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index c16bfdff2953..f1a76bad226e 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4529,6 +4529,19 @@ void nvme_start_freeze(struct nvme_ctrl *ctrl)
 }
 EXPORT_SYMBOL_GPL(nvme_start_freeze);
 
+void nvme_stop_blocking_queues(struct nvme_ctrl *ctrl)
+{
+	struct nvme_ns *ns;
+
+	down_read(&ctrl->namespaces_rwsem);
+	list_for_each_entry(ns, &ctrl->namespaces, list)
+		_blk_mq_quiesce_blocking_queue_async(ns->queue);
+	list_for_each_entry(ns, &ctrl->namespaces, list)
+		_blk_mq_quiesce_blocking_queue_async_wait(ns->queue);
+	up_read(&ctrl->namespaces_rwsem);
+}
+EXPORT_SYMBOL_GPL(nvme_stop_blocking_queues);
+
 void nvme_stop_queues(struct nvme_ctrl *ctrl)
 {
 	struct nvme_ns *ns;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 1609267a1f0e..f8c36176518e 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -568,6 +568,7 @@ int nvme_sec_submit(void *data, u16 spsp, u8 secp, void *buffer, size_t len,
 void nvme_complete_async_event(struct nvme_ctrl *ctrl, __le16 status,
 		volatile union nvme_result *res);
 
+void nvme_stop_blocking_queues(struct nvme_ctrl *ctrl);
 void nvme_stop_queues(struct nvme_ctrl *ctrl);
 void nvme_start_queues(struct nvme_ctrl *ctrl);
 void nvme_kill_queues(struct nvme_ctrl *ctrl);
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 7953362e7bb5..9534626379e7 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1887,6 +1887,7 @@ static void nvme_tcp_teardown_io_queues(struct nvme_ctrl *ctrl,
 {
 	if (ctrl->queue_count <= 1)
 		return;
+	nvme_start_freeze(ctrl);
 	nvme_stop_queues(ctrl);
 	nvme_tcp_stop_io_queues(ctrl);
 	if (ctrl->tagset) {
-- 
2.25.1