mpt2sas: Add free smids to the head, not tail of list

Reusing a smid quickly means it's still cache-hot.  This yields a small
but noticable performance improvement in a well-known database benchmark.
This improvement is already present in the mpt3sas driver.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Reviewed-by: Nicholas Bellinger <nab@linux-iscsi.org>
Reviewed-by: Praveen Krishnamoorthy <Praveen.krishnamoorthy@lsi.com>
Acked-by: Sreekanth Reddy <Sreekanth.reddy@lsi.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/mpt2sas/mpt2sas_base.c

@@ -1739,14 +1739,14 @@ mpt2sas_base_free_smid(struct MPT2SAS_ADAPTER *ioc, u16 smid)
 			list_for_each_entry_safe(chain_req, next,
 			    &ioc->scsi_lookup[i].chain_list, tracker_list) {
 				list_del_init(&chain_req->tracker_list);
-				list_add_tail(&chain_req->tracker_list,
+				list_add(&chain_req->tracker_list,
 				    &ioc->free_chain_list);
 			}
 		}
 		ioc->scsi_lookup[i].cb_idx = 0xFF;
 		ioc->scsi_lookup[i].scmd = NULL;
 		ioc->scsi_lookup[i].direct_io = 0;
-		list_add_tail(&ioc->scsi_lookup[i].tracker_list,
+		list_add(&ioc->scsi_lookup[i].tracker_list,
 		    &ioc->free_list);
 		spin_unlock_irqrestore(&ioc->scsi_lookup_lock, flags);
 
@@ -1764,13 +1764,13 @@ mpt2sas_base_free_smid(struct MPT2SAS_ADAPTER *ioc, u16 smid)
 		/* hi-priority */
 		i = smid - ioc->hi_priority_smid;
 		ioc->hpr_lookup[i].cb_idx = 0xFF;
-		list_add_tail(&ioc->hpr_lookup[i].tracker_list,
+		list_add(&ioc->hpr_lookup[i].tracker_list,
 		    &ioc->hpr_free_list);
 	} else if (smid <= ioc->hba_queue_depth) {
 		/* internal queue */
 		i = smid - ioc->internal_smid;
 		ioc->internal_lookup[i].cb_idx = 0xFF;
-		list_add_tail(&ioc->internal_lookup[i].tracker_list,
+		list_add(&ioc->internal_lookup[i].tracker_list,
 		    &ioc->internal_free_list);
 	}
 	spin_unlock_irqrestore(&ioc->scsi_lookup_lock, flags);