[PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[sbates]

From: Stephen Bates <sbates@raithlin.com>

We should not be using the CMB to determine the permissable q_depth
when we don't plan to place any queues in the CMB. In the case of a
small CMB or large numbers of queues this could lead to shallow queues
when they don't need to be.

Signed-off-by: Stephen Bates <sbates@raithlin.com>
---
 drivers/nvme/host/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 0bc6a9e..0d099e9 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1913,7 +1913,7 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
 	if (nr_io_queues == 0)
 		return 0;
 
-	if (dev->cmb && (dev->cmbsz & NVME_CMBSZ_SQS)) {
+	if (dev->cmb && use_cmb_sqes && (dev->cmbsz & NVME_CMBSZ_SQS)) {
 		result = nvme_cmb_qdepth(dev, nr_io_queues,
 				sizeof(struct nvme_command));
 		if (result > 0)
-- 
2.7.4

[PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[sbates]

From: Stephen Bates <sbates@raithlin.com>

We should not be using the CMB to determine the permissable q_depth
when we don't plan to place any queues in the CMB. In the case of a
small CMB or large numbers of queues this could lead to shallow queues
when they don't need to be.

Signed-off-by: Stephen Bates <sbates at raithlin.com>
---
 drivers/nvme/host/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 0bc6a9e..0d099e9 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1913,7 +1913,7 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
 	if (nr_io_queues == 0)
 		return 0;
 
-	if (dev->cmb && (dev->cmbsz & NVME_CMBSZ_SQS)) {
+	if (dev->cmb && use_cmb_sqes && (dev->cmbsz & NVME_CMBSZ_SQS)) {
 		result = nvme_cmb_qdepth(dev, nr_io_queues,
 				sizeof(struct nvme_command));
 		if (result > 0)
-- 
2.7.4

Re: [PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[Sagi Grimberg]

Looks good,

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

I'll pick this one up unless someone thinks I shouldn't..

[PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[Sagi Grimberg]

Looks good,

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

I'll pick this one up unless someone thinks I shouldn't..

Re: [PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[Max Gurtovoy]

On 2/6/2018 11:48 AM, Sagi Grimberg wrote:
> Looks good,
> 
> Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
> 
> I'll pick this one up unless someone thinks I shouldn't..

Looks good to me (I can imagine what scenario failed this :) ),

Reviewed-by: Max Gurtovoy <maxg@mellanox.com>

> 
> _______________________________________________
> Linux-nvme mailing list
> Linux-nvme@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-nvme

[PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[Max Gurtovoy]

On 2/6/2018 11:48 AM, Sagi Grimberg wrote:
> Looks good,
> 
> Reviewed-by: Sagi Grimberg <sagi at grimberg.me>
> 
> I'll pick this one up unless someone thinks I shouldn't..

Looks good to me (I can imagine what scenario failed this :) ),

Reviewed-by: Max Gurtovoy <maxg at mellanox.com>

> 
> _______________________________________________
> Linux-nvme mailing list
> Linux-nvme at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-nvme

Re: [PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[Keith Busch]

On Mon, Feb 05, 2018 at 03:32:23PM -0700, sbates@raithlin.com wrote:
>  
> -	if (dev->cmb && (dev->cmbsz & NVME_CMBSZ_SQS)) {
> +	if (dev->cmb && use_cmb_sqes && (dev->cmbsz & NVME_CMBSZ_SQS)) {

Is this a prep patch for something coming later? dev->cmb is already
NULL if use_cmb_sqes is false.

[PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[Keith Busch]

On Mon, Feb 05, 2018@03:32:23PM -0700, sbates@raithlin.com wrote:
>  
> -	if (dev->cmb && (dev->cmbsz & NVME_CMBSZ_SQS)) {
> +	if (dev->cmb && use_cmb_sqes && (dev->cmbsz & NVME_CMBSZ_SQS)) {

Is this a prep patch for something coming later? dev->cmb is already
NULL if use_cmb_sqes is false.

Re: [PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[Stephen Bates]

> On Feb 6, 2018, at 8:02 AM, Keith Busch <keith.busch@intel.com> wrote:
> 
>> On Mon, Feb 05, 2018 at 03:32:23PM -0700, sbates@raithlin.com wrote:
>> 
>> -    if (dev->cmb && (dev->cmbsz & NVME_CMBSZ_SQS)) {
>> +    if (dev->cmb && use_cmb_sqes && (dev->cmbsz & NVME_CMBSZ_SQS)) {
> 
> Is this a prep patch for something coming later? dev->cmb is already
> NULL if use_cmb_sqes is false.

Thanks Keith. 

Not sure how I missed this. I was working on OOT patches to enable WDS and RDS in the CMB. I *thought* I’d confirmed this patch was applicable to upstream. Looks like I did not do that correctly. 

Sorry for the churn. We can leave this patch out for now. Thanks for the prompt feedback everyone!

Stephen 

[PATCH] nvme-pci: Fix incorrect use of CMB size to calculate q_depth

[Stephen Bates]

> On Feb 6, 2018,@8:02 AM, Keith Busch <keith.busch@intel.com> wrote:
> 
>> On Mon, Feb 05, 2018@03:32:23PM -0700, sbates@raithlin.com wrote:
>> 
>> -    if (dev->cmb && (dev->cmbsz & NVME_CMBSZ_SQS)) {
>> +    if (dev->cmb && use_cmb_sqes && (dev->cmbsz & NVME_CMBSZ_SQS)) {
> 
> Is this a prep patch for something coming later? dev->cmb is already
> NULL if use_cmb_sqes is false.

Thanks Keith. 

Not sure how I missed this. I was working on OOT patches to enable WDS and RDS in the CMB. I *thought* I?d confirmed this patch was applicable to upstream. Looks like I did not do that correctly. 

Sorry for the churn. We can leave this patch out for now. Thanks for the prompt feedback everyone!

Stephen