[PATCH V4 4/6] nvme: paring quiesce/unquiesce

[Ming Lei]

The current blk_mq_quiesce_queue() and blk_mq_unquiesce_queue() always
stops and starts the queue unconditionally. And there can be concurrent
quiesce/unquiesce coming from different unrelated code paths, so
unquiesce may come unexpectedly and start queue too early.

Prepare for supporting concurrent quiesce/unquiesce from multiple
contexts, so that we can address the above issue.

NVMe has very complicated quiesce/unquiesce use pattern, add one atomic
bit for makeiing sure that blk-mq quiece/unquiesce is always called in
pair.

Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 drivers/nvme/host/core.c | 12 ++++++++----
 drivers/nvme/host/nvme.h |  2 ++
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 23fb746a8970..4391760e2e9a 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4452,12 +4452,14 @@ EXPORT_SYMBOL_GPL(nvme_init_ctrl);
 
 static void nvme_start_ns_queue(struct nvme_ns *ns)
 {
-	blk_mq_unquiesce_queue(ns->queue);
+	if (test_and_clear_bit(NVME_NS_STOPPED, &ns->flags))
+		blk_mq_unquiesce_queue(ns->queue);
 }
 
 static void nvme_stop_ns_queue(struct nvme_ns *ns)
 {
-	blk_mq_quiesce_queue(ns->queue);
+	if (!test_and_set_bit(NVME_NS_STOPPED, &ns->flags))
+		blk_mq_quiesce_queue(ns->queue);
 }
 
 /*
@@ -4575,13 +4577,15 @@ EXPORT_SYMBOL_GPL(nvme_start_queues);
 
 void nvme_stop_admin_queue(struct nvme_ctrl *ctrl)
 {
-	blk_mq_quiesce_queue(ctrl->admin_q);
+	if (!test_and_set_bit(NVME_CTRL_ADMIN_Q_STOPPED, &ctrl->flags))
+		blk_mq_quiesce_queue(ctrl->admin_q);
 }
 EXPORT_SYMBOL_GPL(nvme_stop_admin_queue);
 
 void nvme_start_admin_queue(struct nvme_ctrl *ctrl)
 {
-	blk_mq_unquiesce_queue(ctrl->admin_q);
+	if (test_and_clear_bit(NVME_CTRL_ADMIN_Q_STOPPED, &ctrl->flags))
+		blk_mq_unquiesce_queue(ctrl->admin_q);
 }
 EXPORT_SYMBOL_GPL(nvme_start_admin_queue);
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 47877a5f1515..0fa6fa22f088 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -336,6 +336,7 @@ struct nvme_ctrl {
 	int nr_reconnects;
 	unsigned long flags;
 #define NVME_CTRL_FAILFAST_EXPIRED	0
+#define NVME_CTRL_ADMIN_Q_STOPPED	1
 	struct nvmf_ctrl_options *opts;
 
 	struct page *discard_page;
@@ -457,6 +458,7 @@ struct nvme_ns {
 #define NVME_NS_ANA_PENDING	2
 #define NVME_NS_FORCE_RO	3
 #define NVME_NS_READY		4
+#define NVME_NS_STOPPED		5
 
 	struct cdev		cdev;
 	struct device		cdev_device;
-- 
2.31.1