Do not requeue requests if REQ_FAILFAST is set

Any requests with the REQ_FAILFAST flag set should not be requeued
to the requeust queue, but rather terminated directly.
Otherwise the multipath failover will stall until the command
timeout triggers.

Signed-off-by: Hannes Reinecke <hare@suse.de>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 277f1b6..a12d2f1 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1200,6 +1200,11 @@ static int scsi_prep_fn(struct request_queue *q, struct request *req)
 			 */
 			if (!(req->cmd_flags & REQ_PREEMPT))
 				ret = BLKPREP_DEFER;
+			/*
+			 * Return failfast requests immediately
+			 */
+			if (req->cmd_flags & REQ_FAILFAST)
+				ret = BLKPREP_KILL;
 			break;
 		default:
 			/*
@@ -1327,6 +1332,17 @@ static inline int scsi_host_queue_ready(struct request_queue *q,
 	return 1;
 }
 
+static void __scsi_kill_request(struct request *req)
+{
+	struct scsi_cmnd *cmd = req->special;
+	struct scsi_device *sdev = cmd->device;
+
+	cmd->result = DID_NO_CONNECT << 16;
+	atomic_inc(&cmd->device->iorequest_cnt);
+	sdev->device_busy--;
+	__scsi_done(cmd);
+}
+
 /*
  * Kill a request for a dead device
  */
@@ -1440,8 +1456,16 @@ static void scsi_request_fn(struct request_queue *q)
 		 * accept it.
 		 */
 		req = elv_next_request(q);
-		if (!req || !scsi_dev_queue_ready(q, sdev))
+		if (!req)
+			break;
+
+		if (!scsi_dev_queue_ready(q, sdev)) {
+			if (req->cmd_flags & REQ_FAILFAST) {
+				scsi_kill_request(req, q);
+				continue;
+			}
 			break;
+		}
 
 		if (unlikely(!scsi_device_online(sdev))) {
 			sdev_printk(KERN_ERR, sdev,
@@ -1522,8 +1546,12 @@ static void scsi_request_fn(struct request_queue *q)
 	 * later time.
 	 */
 	spin_lock_irq(q->queue_lock);
-	blk_requeue_request(q, req);
-	sdev->device_busy--;
+	if (unlikely(req->cmd_flags & REQ_FAILFAST))
+		__scsi_kill_request(req);
+	else {
+		blk_requeue_request(q, req);
+		sdev->device_busy--;
+	}
 	if(sdev->device_busy == 0)
 		blk_plug_device(q);
  out: