[SCSI] aic94xx: Don't call pci_map_sg for already-mapped scatterlists

It turns out that libata has already dma_map_sg'd the scatterlist
entries that go with an ata_queued_cmd by the time it calls
sas_ata_qc_issue.  sas_ata_qc_issue passes this scatterlist to aic94xx.
Unfortunately, aic94xx assumes that any scatterlist passed to it needs
to be pci_map_sg'd... which blows away the mapping that libata created!
This causes (on a x260) Calgary IOMMU table leaks and duplicate frees
when aic94xx and libata try to {pci,dma}_unmap_sg the scatterlist.
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>

Key this check off ATA_PROTOCOL_STP
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/aic94xx/aic94xx_task.c

@@ -74,8 +74,13 @@ static inline int asd_map_scatterlist(struct sas_task *task,
 		return 0;
 	}
 
-	num_sg = pci_map_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
-			    task->data_dir);
+	/* STP tasks come from libata which has already mapped
+	 * the SG list */
+	if (task->task_proto == SAS_PROTOCOL_STP)
+		num_sg = task->num_scatter;
+	else
+		num_sg = pci_map_sg(asd_ha->pcidev, task->scatter,
+				    task->num_scatter, task->data_dir);
 	if (num_sg == 0)
 		return -ENOMEM;
 
@@ -120,8 +125,9 @@ static inline int asd_map_scatterlist(struct sas_task *task,
 
 	return 0;
 err_unmap:
-	pci_unmap_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
-		     task->data_dir);
+	if (task->task_proto != SAS_PROTOCOL_STP)
+		pci_unmap_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
+			     task->data_dir);
 	return res;
 }
 
@@ -142,8 +148,9 @@ static inline void asd_unmap_scatterlist(struct asd_ascb *ascb)
 	}
 
 	asd_free_coherent(asd_ha, ascb->sg_arr);
-	pci_unmap_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
-		     task->data_dir);
+	if (task->task_proto != SAS_PROTOCOL_STP)
+		pci_unmap_sg(asd_ha->pcidev, task->scatter, task->num_scatter,
+			     task->data_dir);
 }
 
 /* ---------- Task complete tasklet ---------- */