mpt2sas, mpt3sas: fix upper bound for the module parameter max_sgl_entries

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>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

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;
 	}

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;