[SCSI] esp: tidy up target reference counting

The esp driver currently does hand rolled reference counting of its
target.  It's much easier to do what it needs to do if it's plugged into
the mid-layer callbacks (target_alloc and target_destroy) which were
designed for this case, so do it this way and get rid of the internal
target reference count.
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Stable Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/esp_scsi.c

@@ -2359,6 +2359,24 @@ void scsi_esp_unregister(struct esp *esp)
 }
 EXPORT_SYMBOL(scsi_esp_unregister);
 
+static int esp_target_alloc(struct scsi_target *starget)
+{
+	struct esp *esp = shost_priv(dev_to_shost(&starget->dev));
+	struct esp_target_data *tp = &esp->target[starget->id];
+
+	tp->starget = starget;
+
+	return 0;
+}
+
+static void esp_target_destroy(struct scsi_target *starget)
+{
+	struct esp *esp = shost_priv(dev_to_shost(&starget->dev));
+	struct esp_target_data *tp = &esp->target[starget->id];
+
+	tp->starget = NULL;
+}
+
 static int esp_slave_alloc(struct scsi_device *dev)
 {
 	struct esp *esp = shost_priv(dev->host);
@@ -2370,9 +2388,6 @@ static int esp_slave_alloc(struct scsi_device *dev)
 		return -ENOMEM;
 	dev->hostdata = lp;
 
-	tp->starget = dev->sdev_target;
-	tp->starget_ref++;
-
 	spi_min_period(tp->starget) = esp->min_period;
 	spi_max_offset(tp->starget) = 15;
 
@@ -2426,17 +2441,10 @@ static int esp_slave_configure(struct scsi_device *dev)
 
 static void esp_slave_destroy(struct scsi_device *dev)
 {
-	struct esp *esp = shost_priv(dev->host);
-	struct esp_target_data *tp = &esp->target[dev->id];
 	struct esp_lun_data *lp = dev->hostdata;
 
 	kfree(lp);
 	dev->hostdata = NULL;
-
-	BUG_ON(tp->starget_ref <= 0);
-
-	if (!--tp->starget_ref)
-		tp->starget = NULL;
 }
 
 static int esp_eh_abort_handler(struct scsi_cmnd *cmd)
@@ -2616,6 +2624,8 @@ struct scsi_host_template scsi_esp_template = {
 	.name			= "esp",
 	.info			= esp_info,
 	.queuecommand		= esp_queuecommand,
+	.target_alloc		= esp_target_alloc,
+	.target_destroy		= esp_target_destroy,
 	.slave_alloc		= esp_slave_alloc,
 	.slave_configure	= esp_slave_configure,
 	.slave_destroy		= esp_slave_destroy,

drivers/scsi/esp_scsi.h

@@ -322,7 +322,6 @@ struct esp_target_data {
 	u8			nego_goal_tags;
 
 	struct scsi_target	*starget;
-	int			starget_ref;
 };
 
 struct esp_event_ent {