[PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[Sreekanth Reddy]

1. Removed the upper boundary restriction for the module parameter max_sgl_entries. Earlier, the max_sgl_entries was capped at the SCSI_MAX_SG_SEGMENTS kernel definition. With this change, the user would be able to set the max_sgl_entries to any value.
2. Added a print for the message log whenever the user sets the max_sgl_entries to a value greater than SCSI_MAX_SG_SEGMENTS to warn about the kernel definition overriding.

Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@avagotech.com>
---
 drivers/scsi/mpt2sas/mpt2sas_base.c | 9 ++++++---
 drivers/scsi/mpt3sas/mpt3sas_base.c | 5 ++++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
index 13d1d5b..adb99e5 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_base.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
@@ -2492,9 +2492,12 @@ _base_allocate_memory_pools(struct MPT2SAS_ADAPTER *ioc,  int sleep_flag)
 
 	/* command line tunables  for max sgl entries */
 	if (max_sgl_entries != -1) {
-		ioc->shost->sg_tablesize = (max_sgl_entries <
-		    MPT2SAS_SG_DEPTH) ? max_sgl_entries :
-		    MPT2SAS_SG_DEPTH;
+		if (max_sgl_entries > MPT2SAS_SG_DEPTH)
+			printk(MPT2SAS_WARN_FMT
+			 "setting max_sgl_entries(%d), overriding kernel"
+			 " defined SCSI_MAX_SG_SEGMENTS(%d)\n", ioc->name,
+			  max_sgl_entries, MPT2SAS_SG_DEPTH);
+		ioc->shost->sg_tablesize = max_sgl_entries;
 	} else {
 		ioc->shost->sg_tablesize = MPT2SAS_SG_DEPTH;
 	}
diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index f1918cf..35d4780 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -2667,7 +2667,10 @@ _base_allocate_memory_pools(struct MPT3SAS_ADAPTER *ioc,  int sleep_flag)
 	if (sg_tablesize < MPT3SAS_MIN_PHYS_SEGMENTS)
 		sg_tablesize = MPT3SAS_MIN_PHYS_SEGMENTS;
 	else if (sg_tablesize > MPT3SAS_MAX_PHYS_SEGMENTS)
-		sg_tablesize = MPT3SAS_MAX_PHYS_SEGMENTS;
+		pr_warn(MPT3SAS_FMT
+		 "setting max_sgl_entries(%d), overriding kernel"
+		 " defined SCSI_MAX_SG_SEGMENTS(%d)\n", ioc->name,
+		 max_sgl_entries, MPT3SAS_MAX_PHYS_SEGMENTS);
 	ioc->shost->sg_tablesize = sg_tablesize;
 
 	ioc->hi_priority_depth = facts->HighPriorityCredit;
-- 
2.0.2

Re: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[Martin K. Petersen]

>>>>> "Sreekanth" == Sreekanth Reddy <sreekanth.reddy@avagotech.com> writes:

Sreekanth> 1. Removed the upper boundary restriction for the module
Sreekanth> parameter max_sgl_entries. Earlier, the max_sgl_entries was
Sreekanth> capped at the SCSI_MAX_SG_SEGMENTS kernel definition. With
Sreekanth> this change, the user would be able to set the
Sreekanth> max_sgl_entries to any value.

Shouldn't you be capping at SCSI_MAX_SG_CHAIN_SEGMENTS (or the actual hw
limit)?

-- 
Martin K. Petersen	Oracle Linux Engineering

RE: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[Sreekanth Reddy]

> Shouldn't you be capping at SCSI_MAX_SG_CHAIN_SEGMENTS (or the actual hw
> limit)?

Agreed. And set the Upper limit to SCSI_MAX_SG_CHAIN_SEGMENTS.

Change Set:

1. Extended the upper boundary restriction for the module parameter max_sgl_entries.
   Earlier, the max_sgl_entries was capped at the SCSI_MAX_SG_SEGMENTS kernel definition.
   With this change, the user would be able to set the max_sgl_entries to
   any value which is greater than SCSI_MAX_SG_SEGMENTS and less than the minimum of
   SCSI_MAX_SG_CHAIN_SEGMENTS & hardware limit(Calculated using IOCFacts's MaxChainDepth).

2. Added a print for the message log whenever the user sets the max_sgl_entries to a value
   greater than SCSI_MAX_SG_SEGMENTS to warn about the kernel definition overriding.

Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@avagotech.com>
---
 drivers/scsi/mpt2sas/mpt2sas_base.c | 10 +++++++---
 drivers/scsi/mpt3sas/mpt3sas_base.c | 10 ++++++++--
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
index 58e4521..ca3b564 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_base.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
@@ -2486,9 +2486,13 @@ _base_allocate_memory_pools(struct MPT2SAS_ADAPTER *ioc,  int sleep_flag)
 
 	/* command line tunables  for max sgl entries */
 	if (max_sgl_entries != -1) {
-		ioc->shost->sg_tablesize = (max_sgl_entries <
-		    MPT2SAS_SG_DEPTH) ? max_sgl_entries :
-		    MPT2SAS_SG_DEPTH;
+		if (max_sgl_entries > MPT2SAS_SG_DEPTH)
+			printk(MPT2SAS_WARN_FMT
+			 "setting max_sgl_entries(%d), overriding kernel"
+			 " defined SCSI_MAX_SG_SEGMENTS(%d)\n", ioc->name,
+			  max_sgl_entries, MPT2SAS_SG_DEPTH);
+		ioc->shost->sg_tablesize =  min_t(unsigned short,
+			     max_sgl_entries, SCSI_MAX_SG_CHAIN_SEGMENTS);
 	} else {
 		ioc->shost->sg_tablesize = MPT2SAS_SG_DEPTH;
 	}
diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index 1560115..96db582 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -2659,8 +2659,14 @@ _base_allocate_memory_pools(struct MPT3SAS_ADAPTER *ioc,  int sleep_flag)
 
 	if (sg_tablesize < MPT3SAS_MIN_PHYS_SEGMENTS)
 		sg_tablesize = MPT3SAS_MIN_PHYS_SEGMENTS;
-	else if (sg_tablesize > MPT3SAS_MAX_PHYS_SEGMENTS)
-		sg_tablesize = MPT3SAS_MAX_PHYS_SEGMENTS;
+	else if (sg_tablesize > MPT3SAS_MAX_PHYS_SEGMENTS) {
+		pr_warn(MPT3SAS_FMT
+		 "setting max_sgl_entries(%d), overriding kernel"
+		 " defined SCSI_MAX_SG_SEGMENTS(%d)\n", ioc->name,
+		 max_sgl_entries, MPT3SAS_MAX_PHYS_SEGMENTS);
+		sg_tablesize = min_t(unsigned short, sg_tablesize,
+				      SCSI_MAX_SG_CHAIN_SEGMENTS);
+	}
 	ioc->shost->sg_tablesize = sg_tablesize;
 
 	ioc->hi_priority_depth = facts->HighPriorityCredit;
-- 
2.0.2

Re: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[Martin K. Petersen]

>>>>> "Sreekanth" == Sreekanth Reddy <sreekanth.reddy@avagotech.com> writes:

@@ -2486,9 +2486,13 @@ _base_allocate_memory_pools(struct MPT2SAS_ADAPTER *ioc,  int sleep_flag)
 
 	/* command line tunables  for max sgl entries */
 	if (max_sgl_entries != -1) {
-		ioc->shost->sg_tablesize = (max_sgl_entries <
-		    MPT2SAS_SG_DEPTH) ? max_sgl_entries :
-		    MPT2SAS_SG_DEPTH;
+		if (max_sgl_entries > MPT2SAS_SG_DEPTH)
+			printk(MPT2SAS_WARN_FMT
+			 "setting max_sgl_entries(%d), overriding kernel"
+			 " defined SCSI_MAX_SG_SEGMENTS(%d)\n", ioc->name,
+			  max_sgl_entries, MPT2SAS_SG_DEPTH);
+		ioc->shost->sg_tablesize =  min_t(unsigned short,
+			     max_sgl_entries, SCSI_MAX_SG_CHAIN_SEGMENTS);
 	} else {
 		ioc->shost->sg_tablesize = MPT2SAS_SG_DEPTH;
 	}

Wouldn't it be better to print the new scatterlist limit after it has
been clamped to reflect what it's actually being set to?

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[Sreekanth Reddy]

> @@ -2486,9 +2486,13 @@ _base_allocate_memory_pools(struct MPT2SAS_ADAPTER *ioc,  int sleep_flag)
>
>         /* command line tunables  for max sgl entries */
>         if (max_sgl_entries != -1) {
> -               ioc->shost->sg_tablesize = (max_sgl_entries <
> -                   MPT2SAS_SG_DEPTH) ? max_sgl_entries :
> -                   MPT2SAS_SG_DEPTH;
> +               if (max_sgl_entries > MPT2SAS_SG_DEPTH)
> +                       printk(MPT2SAS_WARN_FMT
> +                        "setting max_sgl_entries(%d), overriding kernel"
> +                        " defined SCSI_MAX_SG_SEGMENTS(%d)\n", ioc->name,
> +                         max_sgl_entries, MPT2SAS_SG_DEPTH);
> +               ioc->shost->sg_tablesize =  min_t(unsigned short,
> +                            max_sgl_entries, SCSI_MAX_SG_CHAIN_SEGMENTS);
>         } else {
>                 ioc->shost->sg_tablesize = MPT2SAS_SG_DEPTH;
>         }
>
> Wouldn't it be better to print the new scatterlist limit after it has
> been clamped to reflect what it's actually being set to?

but Martin, I though to warn the user that the module parameter
max_sgl_entries value what they provided is greater than the kernel
defined SCSI_MAX_SG_SEGMENTS, whether if this module parameter value
is greater than or less than the SCSI_MAX_SG_CHAIN_SEGMENTS. Also I
thought, user may confuse if see observes SCSI_MAX_SG_CHAIN_SEGMENTS
value instead of max_sgl_entries value in the warning message.

Please let me known If my assumption is wrong. Then I will modify this
patch according to your suggestion i.e I will print the scatterlist
limit after it has been clamped.

Thanks,
Sreekanth

Re: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[Martin K. Petersen]

>>>>> "Sreekanth" == Sreekanth Reddy <sreekanth.reddy@avagotech.com> writes:

Sreekanth> I though to warn the user that the module parameter
Sreekanth> max_sgl_entries value what they provided is greater than the
Sreekanth> kernel defined SCSI_MAX_SG_SEGMENTS, whether if this module
Sreekanth> parameter value is greater than or less than the
Sreekanth> SCSI_MAX_SG_CHAIN_SEGMENTS. Also I thought, user may confuse
Sreekanth> if see observes SCSI_MAX_SG_CHAIN_SEGMENTS value instead of
Sreekanth> max_sgl_entries value in the warning message.

I would just prefer to see the value that is in effect. I know what I
provided as override value.

At the very least print a warning if you subsequently clamp the value to
MAX_SG_CHAIN_SEGMENTS. "Requested number of segments %u is bigger than
kernel max %u".

-- 
Martin K. Petersen	Oracle Linux Engineering

RE: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[Sreekanth Reddy]

Hi Martin,

As per your suggestion I have modified the Warning message. Please review the change.
 
Change Set:

1. Extended the upper boundary restriction for the module parameter max_sgl_entries.
   Earlier, the max_sgl_entries was capped at the SCSI_MAX_SG_SEGMENTS kernel definition.
   With this change, the user would be able to set the max_sgl_entries to
   any value which is greater than SCSI_MAX_SG_SEGMENTS and less than the minimum of
   SCSI_MAX_SG_CHAIN_SEGMENTS & hardware limit(Calculated using IOCFacts's MaxChainDepth).

2. Added a print for the message log whenever the user sets the max_sgl_entries to a value
   greater than SCSI_MAX_SG_SEGMENTS to warn about the kernel definition overriding.

Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@avagotech.com>
---
 drivers/scsi/mpt2sas/mpt2sas_base.c | 10 +++++++---
 drivers/scsi/mpt3sas/mpt3sas_base.c | 10 ++++++++--
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
index 13d1d5b..dc088ac 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_base.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
@@ -2492,9 +2492,13 @@ _base_allocate_memory_pools(struct MPT2SAS_ADAPTER *ioc,  int sleep_flag)
 
 	/* command line tunables  for max sgl entries */
 	if (max_sgl_entries != -1) {
-		ioc->shost->sg_tablesize = (max_sgl_entries <
-		    MPT2SAS_SG_DEPTH) ? max_sgl_entries :
-		    MPT2SAS_SG_DEPTH;
+		ioc->shost->sg_tablesize =  min_t(unsigned short,
+			     max_sgl_entries, SCSI_MAX_SG_CHAIN_SEGMENTS);
+		if (ioc->shost->sg_tablesize > MPT2SAS_SG_DEPTH)
+			printk(MPT2SAS_WARN_FMT
+			 "sg_tablesize(%u) is bigger than kernel defined"
+			 " SCSI_MAX_SG_SEGMENTS(%u)\n", ioc->name,
+			  ioc->shost->sg_tablesize, MPT2SAS_SG_DEPTH);
 	} else {
 		ioc->shost->sg_tablesize = MPT2SAS_SG_DEPTH;
 	}
diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index f1918cf..0b8210b 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -2666,8 +2666,14 @@ _base_allocate_memory_pools(struct MPT3SAS_ADAPTER *ioc,  int sleep_flag)
 
 	if (sg_tablesize < MPT3SAS_MIN_PHYS_SEGMENTS)
 		sg_tablesize = MPT3SAS_MIN_PHYS_SEGMENTS;
-	else if (sg_tablesize > MPT3SAS_MAX_PHYS_SEGMENTS)
-		sg_tablesize = MPT3SAS_MAX_PHYS_SEGMENTS;
+	else if (sg_tablesize > MPT3SAS_MAX_PHYS_SEGMENTS) {
+		sg_tablesize = min_t(unsigned short, sg_tablesize,
+				      SCSI_MAX_SG_CHAIN_SEGMENTS);
+		pr_warn(MPT3SAS_FMT
+		 "sg_tablesize(%u) is bigger than kernel"
+		 " defined SCSI_MAX_SG_SEGMENTS(%u)\n", ioc->name,
+		 sg_tablesize, MPT3SAS_MAX_PHYS_SEGMENTS);
+	}
 	ioc->shost->sg_tablesize = sg_tablesize;
 
 	ioc->hi_priority_depth = facts->HighPriorityCredit;
-- 
2.0.2

Re: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl_entries

[Martin K. Petersen]

>>>>> "Sreekanth" == Sreekanth Reddy <sreekanth.reddy@avagotech.com> writes:

Sreekanth> 1. Extended the upper boundary restriction for the module
Sreekanth> parameter max_sgl_entries.  Earlier, the max_sgl_entries was
Sreekanth> capped at the SCSI_MAX_SG_SEGMENTS kernel definition.  With
Sreekanth> this change, the user would be able to set the
Sreekanth> max_sgl_entries to any value which is greater than
Sreekanth> SCSI_MAX_SG_SEGMENTS and less than the minimum of
Sreekanth> SCSI_MAX_SG_CHAIN_SEGMENTS & hardware limit(Calculated using
Sreekanth> IOCFacts's MaxChainDepth).

Sreekanth> 2. Added a print for the message log whenever the user sets
Sreekanth> the max_sgl_entries to a value greater than
Sreekanth> SCSI_MAX_SG_SEGMENTS to warn about the kernel definition
Sreekanth> overriding.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering