scsi: hisi_sas: use atomic64_t for hisi_sas_device.running_req

Sometimes the value of hisi_sas_device.running_req
would go negative unless we have the check for
running_req >= 0 before trying to decrement.

This is because using running_req is not thread-safe.

As such, the value for running_req may be actually incorrect,
so use atomic64_t instead.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Xiang Chen <chenxiang66@hisilicon.com>
Reviewed-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/hisi_sas/hisi_sas.h

@@ -111,7 +111,7 @@ struct hisi_sas_device {
 	struct domain_device	*sas_device;
 	u64 attached_phy;
 	u64 device_id;
-	u64 running_req;
+	atomic64_t running_req;
 	u8 dev_status;
 };
 

drivers/scsi/hisi_sas/hisi_sas_main.c

@@ -162,8 +162,8 @@ static void hisi_sas_slot_abort(struct work_struct *work)
 	hisi_sas_slot_task_free(hisi_hba, task, abort_slot);
 	if (task->task_done)
 		task->task_done(task);
-	if (sas_dev && sas_dev->running_req)
-		sas_dev->running_req--;
+	if (sas_dev)
+		atomic64_dec(&sas_dev->running_req);
 }
 
 static int hisi_sas_task_prep(struct sas_task *task, struct hisi_hba *hisi_hba,
@@ -303,7 +303,7 @@ static int hisi_sas_task_prep(struct sas_task *task, struct hisi_hba *hisi_hba,
 
 	hisi_hba->slot_prep = slot;
 
-	sas_dev->running_req++;
+	atomic64_inc(&sas_dev->running_req);
 	++(*pass);
 
 	return 0;
@@ -1027,7 +1027,8 @@ hisi_sas_internal_abort_task_exec(struct hisi_hba *hisi_hba, u64 device_id,
 
 	hisi_hba->slot_prep = slot;
 
-	sas_dev->running_req++;
+	atomic64_inc(&sas_dev->running_req);
+
 	/* send abort command to our chip */
 	hisi_hba->hw->start_delivery(hisi_hba);
 

drivers/scsi/hisi_sas/hisi_sas_v1_hw.c

@@ -1366,8 +1366,8 @@ static int slot_complete_v1_hw(struct hisi_hba *hisi_hba,
 	}
 
 out:
-	if (sas_dev && sas_dev->running_req)
-		sas_dev->running_req--;
+	if (sas_dev)
+		atomic64_dec(&sas_dev->running_req);
 
 	hisi_sas_slot_task_free(hisi_hba, task, slot);
 	sts = ts->stat;

drivers/scsi/hisi_sas/hisi_sas_v2_hw.c

@@ -1728,8 +1728,8 @@ slot_complete_v2_hw(struct hisi_hba *hisi_hba, struct hisi_sas_slot *slot,
 	}
 
 out:
-	if (sas_dev && sas_dev->running_req)
-		sas_dev->running_req--;
+	if (sas_dev)
+		atomic64_dec(&sas_dev->running_req);
 
 	hisi_sas_slot_task_free(hisi_hba, task, slot);
 	sts = ts->stat;