[SCSI] libiscsi: hook into ramp up/down handling

It is rare to get a queue full with iscsi, because targets seem to
just reduce the iscsi cmd window. However, there is at least
one iscsi target that will throw a queue full when overloaded.
This hooks the iscsi code in to the ramp up/down code, so we
can handle it.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/libiscsi.c

@@ -1739,10 +1739,19 @@ EXPORT_SYMBOL_GPL(iscsi_queuecommand);
 
 int iscsi_change_queue_depth(struct scsi_device *sdev, int depth, int reason)
 {
-	if (reason != SCSI_QDEPTH_DEFAULT)
-		return -EOPNOTSUPP;
-
+	switch (reason) {
+	case SCSI_QDEPTH_DEFAULT:
+		scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
+		break;
+	case SCSI_QDEPTH_QFULL:
+		scsi_track_queue_full(sdev, depth);
+		break;
+	case SCSI_QDEPTH_RAMP_UP:
 		scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
 	return sdev->queue_depth;
 }
 EXPORT_SYMBOL_GPL(iscsi_change_queue_depth);