[IB] fail SA queries if device initialization failed

If the SA query module's initialization fails for a device, then that
device won't have a struct ib_sa_device associated.  We should fail SA
queries in that case, rather than blindly dereferencing the NULL
pointer we get back from ib_get_client_data().
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/sa_query.c

@@ -583,10 +583,16 @@ int ib_sa_path_rec_get(struct ib_device *device, u8 port_num,
 {
 	struct ib_sa_path_query *query;
 	struct ib_sa_device *sa_dev = ib_get_client_data(device, &sa_client);
-	struct ib_sa_port   *port   = &sa_dev->port[port_num - sa_dev->start_port];
-	struct ib_mad_agent *agent  = port->agent;
+	struct ib_sa_port   *port;
+	struct ib_mad_agent *agent;
 	int ret;
 
+	if (!sa_dev)
+		return -ENODEV;
+
+	port  = &sa_dev->port[port_num - sa_dev->start_port];
+	agent = port->agent;
+
 	query = kmalloc(sizeof *query, gfp_mask);
 	if (!query)
 		return -ENOMEM;
@@ -685,10 +691,16 @@ int ib_sa_service_rec_query(struct ib_device *device, u8 port_num, u8 method,
 {
 	struct ib_sa_service_query *query;
 	struct ib_sa_device *sa_dev = ib_get_client_data(device, &sa_client);
-	struct ib_sa_port   *port   = &sa_dev->port[port_num - sa_dev->start_port];
-	struct ib_mad_agent *agent  = port->agent;
+	struct ib_sa_port   *port;
+	struct ib_mad_agent *agent;
 	int ret;
 
+	if (!sa_dev)
+		return -ENODEV;
+
+	port  = &sa_dev->port[port_num - sa_dev->start_port];
+	agent = port->agent;
+
 	if (method != IB_MGMT_METHOD_GET &&
 	    method != IB_MGMT_METHOD_SET &&
 	    method != IB_SA_METHOD_DELETE)
@@ -768,10 +780,16 @@ int ib_sa_mcmember_rec_query(struct ib_device *device, u8 port_num,
 {
 	struct ib_sa_mcmember_query *query;
 	struct ib_sa_device *sa_dev = ib_get_client_data(device, &sa_client);
-	struct ib_sa_port   *port   = &sa_dev->port[port_num - sa_dev->start_port];
-	struct ib_mad_agent *agent  = port->agent;
+	struct ib_sa_port   *port;
+	struct ib_mad_agent *agent;
 	int ret;
 
+	if (!sa_dev)
+		return -ENODEV;
+
+	port  = &sa_dev->port[port_num - sa_dev->start_port];
+	agent = port->agent;
+
 	query = kmalloc(sizeof *query, gfp_mask);
 	if (!query)
 		return -ENOMEM;