[PATCH 2/3] nvme: sanitize KATO setting

[Hannes Reinecke <hare@suse.de>]

According to the NVMe base spec the KATO commands should be sent
at half of the KATO interval, to properly account for round-trip
times.
As we now will only ever send one KATO command per connection we
can easily use the recommended values.
This also fixes a potential issue where the request timeout for
the KATO command does not match the value in the connect command,
which might be causing spurious connection drops from the target.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/nvme/host/core.c    | 9 ++++++---
 drivers/nvme/host/fabrics.c | 2 +-
 drivers/nvme/host/nvme.h    | 9 ++++++++-
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f890b310499e..6d096d41a82f 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1223,7 +1223,8 @@ static void nvme_keep_alive_end_io(struct request *rq, blk_status_t status)
 		startka = true;
 	spin_unlock_irqrestore(&ctrl->lock, flags);
 	if (startka)
-		queue_delayed_work(nvme_wq, &ctrl->ka_work, ctrl->kato * HZ);
+		queue_delayed_work(nvme_wq, &ctrl->ka_work,
+				   NVME_KATO_DELAY(ctrl->kato) * HZ);
 }
 
 static int nvme_keep_alive(struct nvme_ctrl *ctrl)
@@ -1258,7 +1259,8 @@ static void nvme_keep_alive_work(struct work_struct *work)
 		dev_dbg(ctrl->device,
 			"reschedule traffic based keep-alive timer\n");
 		ctrl->comp_seen = false;
-		queue_delayed_work(nvme_wq, &ctrl->ka_work, ctrl->kato * HZ);
+		queue_delayed_work(nvme_wq, &ctrl->ka_work,
+				   NVME_KATO_DELAY(ctrl->kato) * HZ);
 		return;
 	}
 
@@ -1275,7 +1277,8 @@ static void nvme_start_keep_alive(struct nvme_ctrl *ctrl)
 	if (unlikely(ctrl->kato == 0))
 		return;
 
-	queue_delayed_work(nvme_wq, &ctrl->ka_work, ctrl->kato * HZ);
+	queue_delayed_work(nvme_wq, &ctrl->ka_work,
+			   NVME_KATO_DELAY(ctrl->kato) * HZ);
 }
 
 void nvme_stop_keep_alive(struct nvme_ctrl *ctrl)
diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 5dfd806fc2d2..dba32e39afbf 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -382,7 +382,7 @@ int nvmf_connect_admin_queue(struct nvme_ctrl *ctrl)
 	 * and add a grace period for controller kato enforcement
 	 */
 	cmd.connect.kato = ctrl->kato ?
-		cpu_to_le32((ctrl->kato + NVME_KATO_GRACE) * 1000) : 0;
+		cpu_to_le32(ctrl->kato * 1000) : 0;
 
 	if (ctrl->opts->disable_sqflow)
 		cmd.connect.cattr |= NVME_CONNECT_DISABLE_SQFLOW;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 23711f6b7d13..912830389997 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -27,7 +27,14 @@ extern unsigned int admin_timeout;
 #define NVME_ADMIN_TIMEOUT	(admin_timeout * HZ)
 
 #define NVME_DEFAULT_KATO	5
-#define NVME_KATO_GRACE		10
+
+/*
+ * The recommended frequency for KATO commands
+ * according to NVMe 1.4 section 7.12.1:
+ * The host should send Keep Alive commands at half of the
+ * Keep Alive Timeout accounting for transport roundtrip times [..].
+ */
+#define NVME_KATO_DELAY(k)	((k) >> 1)
 
 #ifdef CONFIG_ARCH_NO_SG_CHAIN
 #define  NVME_INLINE_SG_CNT  0
-- 
2.29.2


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