scsi: libfc: do not flood console with messages 'libfc: queue full ...'

When the FCoE sending side becomes congested libfc tries to reduce the
queue depth on the host; however due to the built-in lag before
attempting to ramp down the queue depth _again_ the message log is
flooded with the following message:

	libfc: queue full, reducing can_queue to 512

With this patch the message is printed only once (ie when it's
actually changed).
Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Acked-by: Johannes Thumshirn <jth@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/libfc/fc_fcp.c

@@ -407,11 +407,12 @@ static void fc_fcp_can_queue_ramp_up(struct fc_lport *lport)
  * can_queue. Eventually we will hit the point where we run
  * on all reserved structs.
  */
-static void fc_fcp_can_queue_ramp_down(struct fc_lport *lport)
+static bool fc_fcp_can_queue_ramp_down(struct fc_lport *lport)
 {
 	struct fc_fcp_internal *si = fc_get_scsi_internal(lport);
 	unsigned long flags;
 	int can_queue;
+	bool changed = false;
 
 	spin_lock_irqsave(lport->host->host_lock, flags);
 
@@ -427,9 +428,11 @@ static void fc_fcp_can_queue_ramp_down(struct fc_lport *lport)
 	if (!can_queue)
 		can_queue = 1;
 	lport->host->can_queue = can_queue;
+	changed = true;
 
 unlock:
 	spin_unlock_irqrestore(lport->host->host_lock, flags);
+	return changed;
 }
 
 /*
@@ -1896,11 +1899,11 @@ int fc_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *sc_cmd)
 
 	if (!fc_fcp_lport_queue_ready(lport)) {
 		if (lport->qfull) {
-			fc_fcp_can_queue_ramp_down(lport);
-			shost_printk(KERN_ERR, lport->host,
-				     "libfc: queue full, "
-				     "reducing can_queue to %d.\n",
-				     lport->host->can_queue);
+			if (fc_fcp_can_queue_ramp_down(lport))
+				shost_printk(KERN_ERR, lport->host,
+					     "libfc: queue full, "
+					     "reducing can_queue to %d.\n",
+					     lport->host->can_queue);
 		}
 		rc = SCSI_MLQUEUE_HOST_BUSY;
 		goto out;