[PATCHv2 1/3] Revert "nvme: make keep-alive synchronous operation"

[Nilay Shroff <nilay@linux.ibm.com>]

This reverts commit d06923670b5a5f609603d4a9fee4dec02d38de9c.
This reverts commit 599d9f3a10eec69ef28a90161763e4bd7c9c02bf.

It was realized that the fix implemented to avoid the race
condition between keep alive task and the fabric shutdown code
path in the commit d06923670b5ia ("nvme: make keep-alive
synchronous operation") is not optimal.

We also found that the above race condition is regression caused
due to the changes implemented in commit a54a93d0e359 ("nvme: move
stopping keep-alive into nvme_uninit_ctrl()"). So we decided to
first revert the commit d06923670b5a ("nvme: make keep-alive
synchronous operation") and commit 599d9f3a10ee ("nvme: use helper
nvme_ctrl_state in nvme_keep_alive_finish function") and then fix
the regression.

Link: https://lore.kernel.org/all/196f4013-3bbf-43ff-98b4-9cb2a96c20c2@grimberg.me/
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/host/core.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 84cb859a911d..5016f69e9a15 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1292,12 +1292,14 @@ static void nvme_queue_keep_alive_work(struct nvme_ctrl *ctrl)
 	queue_delayed_work(nvme_wq, &ctrl->ka_work, delay);
 }
 
-static void nvme_keep_alive_finish(struct request *rq,
-		blk_status_t status, struct nvme_ctrl *ctrl)
+static enum rq_end_io_ret nvme_keep_alive_end_io(struct request *rq,
+						 blk_status_t status)
 {
+	struct nvme_ctrl *ctrl = rq->end_io_data;
+	unsigned long flags;
+	bool startka = false;
 	unsigned long rtt = jiffies - (rq->deadline - rq->timeout);
 	unsigned long delay = nvme_keep_alive_work_period(ctrl);
-	enum nvme_ctrl_state state = nvme_ctrl_state(ctrl);
 
 	/*
 	 * Subtract off the keepalive RTT so nvme_keep_alive_work runs
@@ -1311,17 +1313,25 @@ static void nvme_keep_alive_finish(struct request *rq,
 		delay = 0;
 	}
 
+	blk_mq_free_request(rq);
+
 	if (status) {
 		dev_err(ctrl->device,
 			"failed nvme_keep_alive_end_io error=%d\n",
 				status);
-		return;
+		return RQ_END_IO_NONE;
 	}
 
 	ctrl->ka_last_check_time = jiffies;
 	ctrl->comp_seen = false;
-	if (state == NVME_CTRL_LIVE || state == NVME_CTRL_CONNECTING)
+	spin_lock_irqsave(&ctrl->lock, flags);
+	if (ctrl->state == NVME_CTRL_LIVE ||
+	    ctrl->state == NVME_CTRL_CONNECTING)
+		startka = true;
+	spin_unlock_irqrestore(&ctrl->lock, flags);
+	if (startka)
 		queue_delayed_work(nvme_wq, &ctrl->ka_work, delay);
+	return RQ_END_IO_NONE;
 }
 
 static void nvme_keep_alive_work(struct work_struct *work)
@@ -1330,7 +1340,6 @@ static void nvme_keep_alive_work(struct work_struct *work)
 			struct nvme_ctrl, ka_work);
 	bool comp_seen = ctrl->comp_seen;
 	struct request *rq;
-	blk_status_t status;
 
 	ctrl->ka_last_check_time = jiffies;
 
@@ -1353,9 +1362,9 @@ static void nvme_keep_alive_work(struct work_struct *work)
 	nvme_init_request(rq, &ctrl->ka_cmd);
 
 	rq->timeout = ctrl->kato * HZ;
-	status = blk_execute_rq(rq, false);
-	nvme_keep_alive_finish(rq, status, ctrl);
-	blk_mq_free_request(rq);
+	rq->end_io = nvme_keep_alive_end_io;
+	rq->end_io_data = ctrl;
+	blk_execute_rq_nowait(rq, false);
 }
 
 static void nvme_start_keep_alive(struct nvme_ctrl *ctrl)
-- 
2.45.2