[SCSI] zfcp: Defer resource allocation to first ccw_set_online call

So far, zfcp allocated all resources required for FCP
adapters/subchannels when the device was discovered in the ccw_probe
callback. If there are lots of unused FCP subchannels attached to a
system, this is a waste of resources. To alleviate this, defer the
resource allocation to the first call to ccw_set_online. To avoid
disruptions during possible following calls to ccw_set_offline and
then ccw_set_online, keep the adapter resources until the device is
finally being removed via ccw_remove. While doing this, also manage
the zfcp erp thread together with all other adapter resources in
zfcp_adapter_enqueue/dequeue.

Reviewed-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/s390/scsi/zfcp_erp.c

@@ -150,6 +150,9 @@ static int zfcp_erp_required_act(int want, struct zfcp_adapter *adapter,
 		a_status = atomic_read(&adapter->status);
 		if (a_status & ZFCP_STATUS_COMMON_ERP_INUSE)
 			return 0;
+		if (!(a_status & ZFCP_STATUS_COMMON_RUNNING) &&
+		    !(a_status & ZFCP_STATUS_COMMON_OPEN))
+			return 0; /* shutdown requested for closed adapter */
 	}
 
 	return need;
@@ -1349,6 +1352,8 @@ void zfcp_erp_thread_kill(struct zfcp_adapter *adapter)
 {
 	kthread_stop(adapter->erp_thread);
 	adapter->erp_thread = NULL;
+	WARN_ON(!list_empty(&adapter->erp_ready_head));
+	WARN_ON(!list_empty(&adapter->erp_running_head));
 }
 
 /**