[PATCH V2 02/13] scsi: iscsi: Add helper to remove a session from the kernel

[Mike Christie <michael.christie@oracle.com>]

qedi requires that we at least tell the FW to disconnect and cleanup
connections during shutdown, and patch:

commit d1f2ce77638d ("scsi: qedi: Fix host removal with running
sessions")

converted the driver to use the libicsi helper to drive session removal.
The problem is that during shutdown iscsid will not be running so when we
try to remove the root session we will hang wait for userspace to reply.

This patch adds a helper that will drive the destruction of sessions like
these during system shutdown.

Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
 drivers/scsi/scsi_transport_iscsi.c | 54 +++++++++++++++++++++++------
 include/scsi/scsi_transport_iscsi.h |  1 +
 2 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
index e6084e158cc0..cdaa54b6f763 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -2257,16 +2257,8 @@ static void iscsi_if_disconnect_bound_ep(struct iscsi_cls_conn *conn,
 	}
 }
 
-static int iscsi_if_stop_conn(struct iscsi_transport *transport,
-			      struct iscsi_uevent *ev)
+static int iscsi_if_stop_conn(struct iscsi_cls_conn *conn, int flag)
 {
-	int flag = ev->u.stop_conn.flag;
-	struct iscsi_cls_conn *conn;
-
-	conn = iscsi_conn_lookup(ev->u.stop_conn.sid, ev->u.stop_conn.cid);
-	if (!conn)
-		return -EINVAL;
-
 	ISCSI_DBG_TRANS_CONN(conn, "iscsi if conn stop.\n");
 	/*
 	 * If this is a termination we have to call stop_conn with that flag
@@ -2342,6 +2334,43 @@ static void iscsi_cleanup_conn_work_fn(struct work_struct *work)
 	ISCSI_DBG_TRANS_CONN(conn, "cleanup done.\n");
 }
 
+static int iscsi_iter_force_destroy_conn_fn(struct device *dev, void *data)
+{
+	struct iscsi_transport *transport;
+	struct iscsi_cls_conn *conn;
+
+	if (!iscsi_is_conn_dev(dev))
+		return 0;
+
+	conn = iscsi_dev_to_conn(dev);
+	transport = conn->transport;
+
+	if (READ_ONCE(conn->state) != ISCSI_CONN_DOWN)
+		iscsi_if_stop_conn(conn, STOP_CONN_TERM);
+
+	transport->destroy_conn(conn);
+	return 0;
+}
+
+/**
+ * iscsi_force_destroy_session - destroy a session from the kernel
+ * @session: session to destroy
+ *
+ * Force the destruction of a session from the kernel. This should only be
+ * used when userspace is no longer running during system shutdown.
+ */
+void iscsi_force_destroy_session(struct iscsi_cls_session *session)
+{
+	struct iscsi_transport *transport = session->transport;
+
+	WARN_ON_ONCE(system_state == SYSTEM_RUNNING);
+
+	device_for_each_child(&session->dev, NULL,
+			      iscsi_iter_force_destroy_conn_fn);
+	transport->destroy_session(session);
+}
+EXPORT_SYMBOL_GPL(iscsi_force_destroy_session);
+
 void iscsi_free_session(struct iscsi_cls_session *session)
 {
 	ISCSI_DBG_TRANS_SESSION(session, "Freeing session\n");
@@ -3713,7 +3742,12 @@ static int iscsi_if_transport_conn(struct iscsi_transport *transport,
 	case ISCSI_UEVENT_DESTROY_CONN:
 		return iscsi_if_destroy_conn(transport, ev);
 	case ISCSI_UEVENT_STOP_CONN:
-		return iscsi_if_stop_conn(transport, ev);
+		conn = iscsi_conn_lookup(ev->u.stop_conn.sid,
+					 ev->u.stop_conn.cid);
+		if (!conn)
+			return -EINVAL;
+
+		return iscsi_if_stop_conn(conn, ev->u.stop_conn.flag);
 	}
 
 	/*
diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
index 9acb8422f680..d6eab7cb221a 100644
--- a/include/scsi/scsi_transport_iscsi.h
+++ b/include/scsi/scsi_transport_iscsi.h
@@ -442,6 +442,7 @@ extern struct iscsi_cls_session *iscsi_create_session(struct Scsi_Host *shost,
 						struct iscsi_transport *t,
 						int dd_size,
 						unsigned int target_id);
+extern void iscsi_force_destroy_session(struct iscsi_cls_session *session);
 extern void iscsi_remove_session(struct iscsi_cls_session *session);
 extern void iscsi_free_session(struct iscsi_cls_session *session);
 extern struct iscsi_cls_conn *iscsi_alloc_conn(struct iscsi_cls_session *sess,
-- 
2.25.1