[PATCHv3 0/2] nvme: sanitize KATO setting

[PATCHv3 0/2] nvme: sanitize KATO setting

[Hannes Reinecke]

Hi all,

as reserved tag allocation issues are solved with a different patchset,
here are just the bits to sanitize and expose the KATO value to sysfs.
Exposing it to sysfs will allow userspace to identify persistent discovery
controllers (which will have a non-zero KATO value); a patch for that
has been sent to the nvme-cli github repository.

As usual, comments and reviews are welcome.

Hannes Reinecke (2):
  nvme: sanitize KATO setting
  nvme: add 'kato' sysfs attribute

 drivers/nvme/host/core.c    |  8 +++++---
 drivers/nvme/host/fabrics.c |  4 +---
 drivers/nvme/host/nvme.h    | 16 +++++++++++++++-
 3 files changed, 21 insertions(+), 7 deletions(-)

-- 
2.29.2


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[PATCH 1/2] nvme: sanitize KATO setting

[Hannes Reinecke]

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    |  6 +++---
 drivers/nvme/host/fabrics.c |  4 +---
 drivers/nvme/host/nvme.h    | 16 +++++++++++++++-
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 82ad5eef9d0c..b56903982b27 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1223,7 +1223,7 @@ 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);
+		nvme_queue_keep_alive_work(ctrl);
 }
 
 static int nvme_keep_alive(struct nvme_ctrl *ctrl)
@@ -1253,7 +1253,7 @@ 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);
+		nvme_queue_keep_alive_work(ctrl);
 		return;
 	}
 
@@ -1270,7 +1270,7 @@ 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);
+	nvme_queue_keep_alive_work(ctrl);
 }
 
 void nvme_stop_keep_alive(struct nvme_ctrl *ctrl)
diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 604ab0e5a2ad..13c2747e3d00 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -379,10 +379,8 @@ int nvmf_connect_admin_queue(struct nvme_ctrl *ctrl)
 
 	/*
 	 * Set keep-alive timeout in seconds granularity (ms * 1000)
-	 * and add a grace period for controller kato enforcement
 	 */
-	cmd.connect.kato = ctrl->kato ?
-		cpu_to_le32((ctrl->kato + NVME_KATO_GRACE) * 1000) : 0;
+	cmd.connect.kato = cpu_to_le32(ctrl->kato * 1000);
 
 	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 07b34175c6ce..cc74b9f8d5ff 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -27,7 +27,15 @@ extern unsigned int admin_timeout;
 #define NVME_ADMIN_TIMEOUT	(admin_timeout * HZ)
 
 #define NVME_DEFAULT_KATO	5
-#define NVME_KATO_GRACE		10
+
+/*
+ * Recommended frequency for KATO commands
+ *
+ * NVMe 1.4 section 7.12.1 states:
+ * 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)?(k) >> 1:(k))
 
 #ifdef CONFIG_ARCH_NO_SG_CHAIN
 #define  NVME_INLINE_SG_CNT  0
@@ -583,6 +591,12 @@ static inline bool nvme_is_aen_req(u16 qid, __u16 command_id)
 	return !qid && command_id >= NVME_AQ_BLK_MQ_DEPTH;
 }
 
+static inline void nvme_queue_keep_alive_work(struct nvme_ctrl *ctrl)
+{
+	queue_delayed_work(nvme_wq, &ctrl->ka_work,
+			   NVME_KATO_DELAY(ctrl->kato * HZ));
+}
+
 void nvme_complete_rq(struct request *req);
 blk_status_t nvme_host_path_error(struct request *req);
 bool nvme_cancel_request(struct request *req, void *data, bool reserved);
-- 
2.29.2


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[PATCH 2/2] nvme: add 'kato' sysfs attribute

[Hannes Reinecke]

Add a 'kato' controller sysfs attribute to display the current
keep-alive timeout value (if any). This allows userspace to identify
persistent discovery controllers, as these will have a non-zero
KATO value.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index b56903982b27..206e6f883ca8 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3540,6 +3540,7 @@ nvme_show_int_function(cntlid);
 nvme_show_int_function(numa_node);
 nvme_show_int_function(queue_count);
 nvme_show_int_function(sqsize);
+nvme_show_int_function(kato);
 
 static ssize_t nvme_sysfs_delete(struct device *dev,
 				struct device_attribute *attr, const char *buf,
@@ -3706,6 +3707,7 @@ static struct attribute *nvme_dev_attrs[] = {
 	&dev_attr_hostid.attr,
 	&dev_attr_ctrl_loss_tmo.attr,
 	&dev_attr_reconnect_delay.attr,
+	&dev_attr_kato.attr,
 	NULL
 };
 
-- 
2.29.2


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Re: [PATCH 1/2] nvme: sanitize KATO setting

[Christoph Hellwig]

> +/*
> + * Recommended frequency for KATO commands
> + *
> + * NVMe 1.4 section 7.12.1 states:
> + * 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)?(k) >> 1:(k))

This should have been an inline if added at all, and use proper
formatting, as well as avoiding the shift obsfucation.

I think the best is to just move this into the only caller, where
we also know that ctrl->kato can't be 0 due to the check in
nvme_start_keep_alive:

/*
 * Recommended frequency for KATO commands per  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 [..].
*/
static inline void nvme_queue_keep_alive_work(struct nvme_ctrl *ctrl)
{
	queue_delayed_work(nvme_wq, &ctrl->ka_work, ctrl->kato * HZ / 2);
}

Also please keep this helper inside of core.c.

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Re: [PATCH 2/2] nvme: add 'kato' sysfs attribute

[Sagi Grimberg]

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

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Re: [PATCH 1/2] nvme: sanitize KATO setting

[Sagi Grimberg]

On 3/11/21 2:55 AM, Christoph Hellwig wrote:
>> +/*
>> + * Recommended frequency for KATO commands
>> + *
>> + * NVMe 1.4 section 7.12.1 states:
>> + * 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)?(k) >> 1:(k))
> 
> This should have been an inline if added at all, and use proper
> formatting, as well as avoiding the shift obsfucation.
> 
> I think the best is to just move this into the only caller, where
> we also know that ctrl->kato can't be 0 due to the check in
> nvme_start_keep_alive:
> 
> /*
>   * Recommended frequency for KATO commands per  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 [..].
> */
> static inline void nvme_queue_keep_alive_work(struct nvme_ctrl *ctrl)
> {
> 	queue_delayed_work(nvme_wq, &ctrl->ka_work, ctrl->kato * HZ / 2);
> }
> 
> Also please keep this helper inside of core.c.

Agreed.

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[PATCH 1/2] nvme: sanitize KATO setting

[Hannes Reinecke]

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    | 18 +++++++++++++++---
 drivers/nvme/host/fabrics.c |  4 +---
 drivers/nvme/host/nvme.h    |  1 -
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 40f08e6325ef..f58e196d5b4b 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1109,6 +1109,18 @@ void nvme_execute_passthru_rq(struct request *rq)
 }
 EXPORT_SYMBOL_NS_GPL(nvme_execute_passthru_rq, NVME_TARGET_PASSTHRU);
 
+/*
+ * Recommended frequency for KATO commands per 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 [..].
+ */
+static inline void nvme_queue_keep_alive_work(struct nvme_ctrl *ctrl)
+{
+	queue_delayed_work(nvme_wq, &ctrl->ka_work,
+			   ctrl->kato * HZ / 2);
+}
+
 static void nvme_keep_alive_end_io(struct request *rq, blk_status_t status)
 {
 	struct nvme_ctrl *ctrl = rq->end_io_data;
@@ -1131,7 +1143,7 @@ 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);
+		nvme_queue_keep_alive_work(ctrl);
 }
 
 static int nvme_keep_alive(struct nvme_ctrl *ctrl)
@@ -1161,7 +1173,7 @@ 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);
+		nvme_queue_keep_alive_work(ctrl);
 		return;
 	}
 
@@ -1178,7 +1190,7 @@ 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);
+	nvme_queue_keep_alive_work(ctrl);
 }
 
 void nvme_stop_keep_alive(struct nvme_ctrl *ctrl)
diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 604ab0e5a2ad..13c2747e3d00 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -379,10 +379,8 @@ int nvmf_connect_admin_queue(struct nvme_ctrl *ctrl)
 
 	/*
 	 * Set keep-alive timeout in seconds granularity (ms * 1000)
-	 * and add a grace period for controller kato enforcement
 	 */
-	cmd.connect.kato = ctrl->kato ?
-		cpu_to_le32((ctrl->kato + NVME_KATO_GRACE) * 1000) : 0;
+	cmd.connect.kato = cpu_to_le32(ctrl->kato * 1000);
 
 	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 c6102ce83bb4..49276186d5bd 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -27,7 +27,6 @@ extern unsigned int admin_timeout;
 #define NVME_ADMIN_TIMEOUT	(admin_timeout * HZ)
 
 #define NVME_DEFAULT_KATO	5
-#define NVME_KATO_GRACE		10
 
 #ifdef CONFIG_ARCH_NO_SG_CHAIN
 #define  NVME_INLINE_SG_CNT  0
-- 
2.29.2


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