[PATCH] 4/7 cleanup/consolidate code in scsi_request_fn

Cleanup and consolidate scsi_device and scsi_host checks in
scsi_request_fn.

drivers/scsi/scsi_lib.c

@@ -1042,6 +1042,79 @@ static int scsi_prep_fn(struct request_queue *q, struct request *req)
 	return BLKPREP_OK;
 }
 
+/*
+ * scsi_check_sdev: if we can send requests to sdev, return 0 else return 1.
+ *
+ * Called with the queue_lock held.
+ */
+static inline int scsi_check_sdev(struct request_queue *q,
+				  struct scsi_device *sdev)
+{
+	if (sdev->device_busy >= sdev->queue_depth)
+		return 1;
+	if (sdev->device_busy == 0 && sdev->device_blocked) {
+		/*
+		 * unblock after device_blocked iterates to zero
+		 */
+		if (--sdev->device_blocked == 0) {
+			SCSI_LOG_MLQUEUE(3,
+				printk("scsi%d (%d:%d) unblocking device at"
+				       " zero depth\n", sdev->host->host_no,
+				       sdev->id, sdev->lun));
+		} else {
+			blk_plug_device(q);
+			return 1;
+		}
+	}
+	if (sdev->device_blocked)
+		return 1;
+
+	return 0;
+}
+
+/*
+ * scsi_check_shost: if we can send requests to shost, return 0 else return 1.
+ *
+ * Called with the queue_lock held.
+ */
+static inline int scsi_check_shost(struct request_queue *q,
+				   struct Scsi_Host *shost,
+				   struct scsi_device *sdev)
+{
+	if (shost->in_recovery)
+		return 1;
+	if (shost->host_busy == 0 && shost->host_blocked) {
+		/*
+		 * unblock after host_blocked iterates to zero
+		 */
+		if (--shost->host_blocked == 0) {
+			SCSI_LOG_MLQUEUE(3,
+				printk("scsi%d unblocking host at zero depth\n",
+					shost->host_no));
+		} else {
+			blk_plug_device(q);
+			return 1;
+		}
+	}
+	if (!list_empty(&sdev->starved_entry))
+		return 1;
+	if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
+	    shost->host_blocked || shost->host_self_blocked) {
+		SCSI_LOG_MLQUEUE(3,
+			printk("add starved dev <%d,%d,%d,%d>; host "
+			       "limit %d, busy %d, blocked %d selfblocked %d\n",
+			       sdev->host->host_no, sdev->channel,
+			       sdev->id, sdev->lun,
+			       shost->can_queue, shost->host_busy,
+			       shost->host_blocked, shost->host_self_blocked));
+		list_add_tail(&sdev->starved_entry,
+			      &shost->starved_list);
+		return 1;
+	}
+
+	return 0;
+}
+
 /*
  * Function:    scsi_request_fn()
  *
@@ -1067,13 +1140,8 @@ static void scsi_request_fn(request_queue_t *q)
 	 * the host is no longer able to accept any more requests.
 	 */
 	for (;;) {
-		/*
-		 * Check this again - each time we loop through we will have
-		 * released the lock and grabbed it again, so each time
-		 * we need to check to see if the queue is plugged or not.
-		 */
-		if (shost->in_recovery || blk_queue_plugged(q))
-			return;
+		if (blk_queue_plugged(q))
+			break;
 
 		/*
 		 * get next queueable request.  We do this early to make sure
@@ -1083,49 +1151,12 @@ static void scsi_request_fn(request_queue_t *q)
 		 */
 		req = elv_next_request(q);
 
-		if (sdev->device_busy >= sdev->queue_depth)
+		if (scsi_check_sdev(q, sdev))
 			break;
 
-		if (shost->host_busy == 0 && shost->host_blocked) {
-			/* unblock after host_blocked iterates to zero */
-			if (--shost->host_blocked == 0) {
-				SCSI_LOG_MLQUEUE(3,
-					printk("scsi%d unblocking host at zero depth\n",
-						shost->host_no));
-			} else {
-				blk_plug_device(q);
-				break;
-			}
-		}
-
-		if (sdev->device_busy == 0 && sdev->device_blocked) {
-			/* unblock after device_blocked iterates to zero */
-			if (--sdev->device_blocked == 0) {
-				SCSI_LOG_MLQUEUE(3,
-					printk("scsi%d (%d:%d) unblocking device at zero depth\n",
-						shost->host_no, sdev->id, sdev->lun));
-			} else {
-				blk_plug_device(q);
-				break;
-			}
-		}
-
-		/*
-		 * If the device cannot accept another request, then quit.
-		 */
-		if (sdev->device_blocked)
-			break;
-
-		if (!list_empty(&sdev->starved_entry))
+		if (scsi_check_shost(q, shost, sdev))
 			break;
 
-		if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
-		    shost->host_blocked || shost->host_self_blocked) {
-			list_add_tail(&sdev->starved_entry,
-				      &shost->starved_list);
-			break;
-		}
-
 		if (sdev->single_lun && scsi_single_lun_check(sdev))
 			break;
 
@@ -1140,7 +1171,7 @@ static void scsi_request_fn(request_queue_t *q)
 			/* If the device is busy, a returning I/O
 			 * will restart the queue.  Otherwise, we have
 			 * to plug the queue */
-			if(sdev->device_busy == 0)
+			if (sdev->device_busy == 0)
 				blk_plug_device(q);
 			break;
 		}