[SCSI] iscsi class: add async scan helper

In qla4xxx's probe it will call the iscsi session setup functions
for session that got setup on the initial start. This then makes
it easy for the iscsi class to export a helper which indicates
when those scans are done.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/scsi_transport_iscsi.c

@@ -127,6 +127,7 @@ static int iscsi_setup_host(struct transport_container *tc, struct device *dev,
 	memset(ihost, 0, sizeof(*ihost));
 	INIT_LIST_HEAD(&ihost->sessions);
 	mutex_init(&ihost->mutex);
+	atomic_set(&ihost->nr_scans, 0);
 
 	snprintf(ihost->scan_workq_name, KOBJ_NAME_LEN, "iscsi_scan_%d",
 		shost->host_no);
@@ -284,6 +285,25 @@ static int iscsi_is_session_dev(const struct device *dev)
 	return dev->release == iscsi_session_release;
 }
 
+/**
+ * iscsi_scan_finished - helper to report when running scans are done
+ * @shost: scsi host
+ * @time: scan run time
+ *
+ * This function can be used by drives like qla4xxx to report to the scsi
+ * layer when the scans it kicked off at module load time are done.
+ */
+int iscsi_scan_finished(struct Scsi_Host *shost, unsigned long time)
+{
+	struct iscsi_host *ihost = shost->shost_data;
+	/*
+	 * qla4xxx will have kicked off some session unblocks before calling
+	 * scsi_scan_host, so just wait for them to complete.
+	 */
+	return !atomic_read(&ihost->nr_scans);
+}
+EXPORT_SYMBOL_GPL(iscsi_scan_finished);
+
 static int iscsi_user_scan(struct Scsi_Host *shost, uint channel,
 			   uint id, uint lun)
 {
@@ -306,17 +326,21 @@ static void iscsi_scan_session(struct work_struct *work)
 {
 	struct iscsi_cls_session *session =
 			container_of(work, struct iscsi_cls_session, scan_work);
+	struct Scsi_Host *shost = iscsi_session_to_shost(session);
+	struct iscsi_host *ihost = shost->shost_data;
 	unsigned long flags;
 
 	spin_lock_irqsave(&session->lock, flags);
 	if (session->state != ISCSI_SESSION_LOGGED_IN) {
 		spin_unlock_irqrestore(&session->lock, flags);
-		return;
+		goto done;
 	}
 	spin_unlock_irqrestore(&session->lock, flags);
 
 	scsi_scan_target(&session->dev, 0, session->target_id,
 			 SCAN_WILD_CARD, 1);
+done:
+	atomic_dec(&ihost->nr_scans);
 }
 
 static void session_recovery_timedout(struct work_struct *work)
@@ -366,7 +390,15 @@ void iscsi_unblock_session(struct iscsi_cls_session *session)
 	spin_unlock_irqrestore(&session->lock, flags);
 
 	__iscsi_unblock_session(session);
-	queue_work(ihost->scan_workq, &session->scan_work);
+	/*
+	 * Only do kernel scanning if the driver is properly hooked into
+	 * the async scanning code (drivers like iscsi_tcp do login and
+	 * scanning from userspace).
+	 */
+	if (shost->hostt->scan_finished) {
+		if (queue_work(ihost->scan_workq, &session->scan_work))
+			atomic_inc(&ihost->nr_scans);
+	}
 }
 EXPORT_SYMBOL_GPL(iscsi_unblock_session);
 
@@ -550,7 +582,7 @@ void iscsi_remove_session(struct iscsi_cls_session *session)
 	session->state = ISCSI_SESSION_FREE;
 	spin_unlock_irqrestore(&session->lock, flags);
 	__iscsi_unblock_session(session);
-	iscsi_unbind_session(session);
+	__iscsi_unbind_session(&session->unbind_work);
 
 	/* flush running scans */
 	flush_workqueue(ihost->scan_workq);

include/scsi/scsi_transport_iscsi.h

@@ -203,6 +203,7 @@ struct iscsi_cls_session {
 
 struct iscsi_host {
 	struct list_head sessions;
+	atomic_t nr_scans;
 	struct mutex mutex;
 	struct workqueue_struct *scan_workq;
 	char scan_workq_name[KOBJ_NAME_LEN];
@@ -229,6 +230,6 @@ extern struct iscsi_cls_conn *iscsi_create_conn(struct iscsi_cls_session *sess,
 extern int iscsi_destroy_conn(struct iscsi_cls_conn *conn);
 extern void iscsi_unblock_session(struct iscsi_cls_session *session);
 extern void iscsi_block_session(struct iscsi_cls_session *session);
-
+extern int iscsi_scan_finished(struct Scsi_Host *shost, unsigned long time);
 
 #endif