[PATCH 0/2] nvme: prevent warning triggered by nvme_stop_keep_alive

[PATCH 0/2] nvme: prevent warning triggered by nvme_stop_keep_alive

[James Smart]

Delayed keep alive work is queued on system workqueue and may be cancelled 
via nvme_stop_keep_alive from nvme_reset_wq, nvme_fc_wq or nvme_wq.

Check_flush_dependency detects mismatched attributes between the work-queue
context used to cancel the keep alive work and system-wq. Specifically
system-wq does not have the WQ_MEM_RECLAIM flag, whereas the contexts used
to cancel keep alive work have WQ_MEM_RECLAIM flag.

Example warning:

  workqueue: WQ_MEM_RECLAIM nvme-reset-wq:nvme_fc_reset_ctrl_work [nvme_fc]
	is flushing !WQ_MEM_RECLAIM events:nvme_keep_alive_work [nvme_core]

To avoid the flags mismatch, delayed keep alive work is queued on nvme_wq. 

However this creates a secondary concern where work and a request to cancel
that work may be in the same work queue - namely err_work in the rdma and
tcp transports, which will want to flush/cancel the keep alive work which
will now be on nvme_wq.

After reviewing the transports, it looks like err_work can be moved to
nvme_reset_wq. In fact that aligns them better with transition into
RESETTING and performing related reset work in nvme_reset_wq.


James Smart (2):
  nvme: move keep alive processing to nvme-wq
  nvme-rdma/nvme-tcp: Move err_work to nvme_reset_wq

 drivers/nvme/host/core.c | 10 +++++-----
 drivers/nvme/host/rdma.c |  2 +-
 drivers/nvme/host/tcp.c  |  2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

-- 
2.13.7


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[PATCH 1/2] nvme: move keep alive processing to nvme-wq

[James Smart]

Delayed keep alive work is queued on system workqueue and may be cancelled
via nvme_stop_keep_alive from nvme-reset-wq, nvme-fc-wq or nvme-wq.

Check_flush_dependency detects mismatched attributes between the work-queue
context used to cancel the keep alive work and system-wq. Specifically
system-wq does not have the WQ_MEM_RECLAIM flag, whereas the contexts used
to cancel keep alive work have WQ_MEM_RECLAIM flag.

Example warning:

  workqueue: WQ_MEM_RECLAIM nvme-reset-wq:nvme_fc_reset_ctrl_work [nvme_fc]
	is flushing !WQ_MEM_RECLAIM events:nvme_keep_alive_work [nvme_core]

To avoid the flags mismatch, move keep alive work to nvme-wq.

Signed-off-by: Nigel Kirkland <nigel.kirkland@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
---
 drivers/nvme/host/core.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 6ec03507da68..303b308fde52 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -66,8 +66,8 @@ MODULE_PARM_DESC(streams, "turn on support for Streams write directives");
  * nvme_reset_wq - hosts nvme reset works
  * nvme_delete_wq - hosts nvme delete works
  *
- * nvme_wq will host works such are scan, aen handling, fw activation,
- * keep-alive error recovery, periodic reconnects etc. nvme_reset_wq
+ * nvme_wq will host works such as scan, aen handling, fw activation,
+ * keep-alive, periodic reconnects etc. nvme_reset_wq
  * runs reset works which also flush works hosted on nvme_wq for
  * serialization purposes. nvme_delete_wq host controller deletion
  * works which flush reset works for serialization.
@@ -974,7 +974,7 @@ static void nvme_keep_alive_end_io(struct request *rq, blk_status_t status)
 		startka = true;
 	spin_unlock_irqrestore(&ctrl->lock, flags);
 	if (startka)
-		schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
+		queue_delayed_work(nvme_wq, &ctrl->ka_work, ctrl->kato * HZ);
 }
 
 static int nvme_keep_alive(struct nvme_ctrl *ctrl)
@@ -1004,7 +1004,7 @@ 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;
-		schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
+		queue_delayed_work(nvme_wq, &ctrl->ka_work, ctrl->kato * HZ);
 		return;
 	}
 
@@ -1021,7 +1021,7 @@ static void nvme_start_keep_alive(struct nvme_ctrl *ctrl)
 	if (unlikely(ctrl->kato == 0))
 		return;
 
-	schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
+	queue_delayed_work(nvme_wq, &ctrl->ka_work, ctrl->kato * HZ);
 }
 
 void nvme_stop_keep_alive(struct nvme_ctrl *ctrl)
-- 
2.13.7


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Re: [PATCH 1/2] nvme: move keep alive processing to nvme-wq

[Sagi Grimberg]

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

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Re: [PATCH 1/2] nvme: move keep alive processing to nvme-wq

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

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Re: [PATCH 1/2] nvme: move keep alive processing to nvme-wq

[Keith Busch]

On Thu, Feb 06, 2020 at 11:13:41AM -0800, James Smart wrote:
> Delayed keep alive work is queued on system workqueue and may be cancelled
> via nvme_stop_keep_alive from nvme-reset-wq, nvme-fc-wq or nvme-wq.
> 
> Check_flush_dependency detects mismatched attributes between the work-queue
> context used to cancel the keep alive work and system-wq. Specifically
> system-wq does not have the WQ_MEM_RECLAIM flag, whereas the contexts used
> to cancel keep alive work have WQ_MEM_RECLAIM flag.
> 
> Example warning:
> 
>   workqueue: WQ_MEM_RECLAIM nvme-reset-wq:nvme_fc_reset_ctrl_work [nvme_fc]
> 	is flushing !WQ_MEM_RECLAIM events:nvme_keep_alive_work [nvme_core]
> 
> To avoid the flags mismatch, move keep alive work to nvme-wq.
> 
> Signed-off-by: Nigel Kirkland <nigel.kirkland@broadcom.com>
> Signed-off-by: James Smart <jsmart2021@gmail.com>

Hi James,

I'd like to include this in the next 5.6-rc pull, but just want to
clarify attribution: the author should be the first sign-off, so
should I amend the author to Nigel or move his sign-off below yours?

Thanks,
Keith

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Re: [PATCH 1/2] nvme: move keep alive processing to nvme-wq

[James Smart]

On 2/10/2020 7:00 PM, Keith Busch wrote:
> On Thu, Feb 06, 2020 at 11:13:41AM -0800, James Smart wrote:
>> Delayed keep alive work is queued on system workqueue and may be cancelled
>> via nvme_stop_keep_alive from nvme-reset-wq, nvme-fc-wq or nvme-wq.
>>
>> Check_flush_dependency detects mismatched attributes between the work-queue
>> context used to cancel the keep alive work and system-wq. Specifically
>> system-wq does not have the WQ_MEM_RECLAIM flag, whereas the contexts used
>> to cancel keep alive work have WQ_MEM_RECLAIM flag.
>>
>> Example warning:
>>
>>    workqueue: WQ_MEM_RECLAIM nvme-reset-wq:nvme_fc_reset_ctrl_work [nvme_fc]
>> 	is flushing !WQ_MEM_RECLAIM events:nvme_keep_alive_work [nvme_core]
>>
>> To avoid the flags mismatch, move keep alive work to nvme-wq.
>>
>> Signed-off-by: Nigel Kirkland <nigel.kirkland@broadcom.com>
>> Signed-off-by: James Smart <jsmart2021@gmail.com>
> 
> Hi James,
> 
> I'd like to include this in the next 5.6-rc pull, but just want to
> clarify attribution: the author should be the first sign-off, so
> should I amend the author to Nigel or move his sign-off below yours?
> 
> Thanks,
> Keith
> 

either of us as author is fine. so just pull it and have Nigel be author.

-- james


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[PATCH 2/2] nvme-rdma/nvme-tcp: Move err_work to nvme_reset_wq

[James Smart]

With keep alive processing being moved to nvme_wq, it potentially creates
a conflicting position with err_work also processing on nvme_wq and needing
to flush/stop keep alives.

To avoid issues, schedule err_work on nvme_reset_wq. It looks like this is
not only a good thing for keep alives, but also brings the transports in
line with the RESETTING state and processing work relative to RESETTING
on nvme_reset_wq.

This change is made to both nvme-rdma and nvme-tcp which have like code.

Signed-off-by: Nigel Kirkland <nigel.kirkland@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
---
 drivers/nvme/host/rdma.c | 2 +-
 drivers/nvme/host/tcp.c  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 2a47c6c5007e..3e85c5cacefd 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1088,7 +1088,7 @@ static void nvme_rdma_error_recovery(struct nvme_rdma_ctrl *ctrl)
 	if (!nvme_change_ctrl_state(&ctrl->ctrl, NVME_CTRL_RESETTING))
 		return;
 
-	queue_work(nvme_wq, &ctrl->err_work);
+	queue_work(nvme_reset_wq, &ctrl->err_work);
 }
 
 static void nvme_rdma_wr_error(struct ib_cq *cq, struct ib_wc *wc,
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 6d43b23a0fc8..a28f9144954c 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -422,7 +422,7 @@ static void nvme_tcp_error_recovery(struct nvme_ctrl *ctrl)
 	if (!nvme_change_ctrl_state(ctrl, NVME_CTRL_RESETTING))
 		return;
 
-	queue_work(nvme_wq, &to_tcp_ctrl(ctrl)->err_work);
+	queue_work(nvme_reset_wq, &to_tcp_ctrl(ctrl)->err_work);
 }
 
 static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
-- 
2.13.7


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Re: [PATCH 2/2] nvme-rdma/nvme-tcp: Move err_work to nvme_reset_wq

[Sagi Grimberg]

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

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Re: [PATCH 2/2] nvme-rdma/nvme-tcp: Move err_work to nvme_reset_wq

[Christoph Hellwig]

On Thu, Feb 06, 2020 at 11:13:42AM -0800, James Smart wrote:
> With keep alive processing being moved to nvme_wq, it potentially creates
> a conflicting position with err_work also processing on nvme_wq and needing
> to flush/stop keep alives.
> 
> To avoid issues, schedule err_work on nvme_reset_wq. It looks like this is
> not only a good thing for keep alives, but also brings the transports in
> line with the RESETTING state and processing work relative to RESETTING
> on nvme_reset_wq.
> 
> This change is made to both nvme-rdma and nvme-tcp which have like code.

Shouldn't we move both in one patch to create a regression in one
cycle while fixing the other one?

Otherwise this looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

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Re: [PATCH 2/2] nvme-rdma/nvme-tcp: Move err_work to nvme_reset_wq

[Max Gurtovoy]

On 2/10/2020 7:04 PM, Christoph Hellwig wrote:
> On Thu, Feb 06, 2020 at 11:13:42AM -0800, James Smart wrote:
>> With keep alive processing being moved to nvme_wq, it potentially creates
>> a conflicting position with err_work also processing on nvme_wq and needing
>> to flush/stop keep alives.
>>
>> To avoid issues, schedule err_work on nvme_reset_wq. It looks like this is
>> not only a good thing for keep alives, but also brings the transports in
>> line with the RESETTING state and processing work relative to RESETTING
>> on nvme_reset_wq.
>>
>> This change is made to both nvme-rdma and nvme-tcp which have like code.
> Shouldn't we move both in one patch to create a regression in one
> cycle while fixing the other one?

Yup, seems like these should be squashed.

James,

did you run some testing for RDMA/tcp that will trigger this code ?

Fio + port toggling for example ?

or brutally "killing" target during traffic that will cause timeouts to 
IOs ?


>
> Otherwise this looks good:
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

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Re: [PATCH 2/2] nvme-rdma/nvme-tcp: Move err_work to nvme_reset_wq

[James Smart]

On 2/11/2020 2:12 AM, Max Gurtovoy wrote:
> 
> On 2/10/2020 7:04 PM, Christoph Hellwig wrote:
>> On Thu, Feb 06, 2020 at 11:13:42AM -0800, James Smart wrote:
>>> With keep alive processing being moved to nvme_wq, it potentially 
>>> creates
>>> a conflicting position with err_work also processing on nvme_wq and 
>>> needing
>>> to flush/stop keep alives.
>>>
>>> To avoid issues, schedule err_work on nvme_reset_wq. It looks like 
>>> this is
>>> not only a good thing for keep alives, but also brings the transports in
>>> line with the RESETTING state and processing work relative to RESETTING
>>> on nvme_reset_wq.
>>>
>>> This change is made to both nvme-rdma and nvme-tcp which have like code.
>> Shouldn't we move both in one patch to create a regression in one
>> cycle while fixing the other one?
> 
> Yup, seems like these should be squashed.

note: see the v2 posted yesterday.

> 
> James,
> 
> did you run some testing for RDMA/tcp that will trigger this code ?

The testing of the keepalive movement was all in FC. FC already has it's 
calls from either nvme_reset_wq or nvme_delete_wq.

For RDMA/TCP - it was not tested. It was by code inspection and looking 
at who calls the keepalive cancellation calls.

-- james


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