net: rmnet_data: Add NAPI context for rmnet_data devices

This is needed so that we can pass the virtual netdevice NAPI struct
to napi_gro_receive rather than relying on the current CPU NAPI
context which can cause issues due to CPU hotplug.

Change-Id: I41977c3a3a51212aa2fe092427b0ca924045b477
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>

net/rmnet_data/rmnet_data_handlers.c

@@ -212,14 +212,10 @@ static rx_handler_result_t __rmnet_deliver_skb(struct sk_buff *skb,
 			skb->pkt_type = PACKET_HOST;
 			rmnet_reset_mac_header(skb);
 			if (skb->dev->features & NETIF_F_GRO) {
-				napi = get_current_napi_context();
-				if (napi != NULL) {
-					gro_res = napi_gro_receive(napi, skb);
-					trace_rmnet_gro_downlink(gro_res);
-				} else {
-					WARN_ONCE(1, "current napi is NULL\n");
-					netif_receive_skb(skb);
-				}
+				napi = rmnet_vnd_get_napi(skb->dev);
+				napi_schedule(napi);
+				gro_res = napi_gro_receive(napi, skb);
+				trace_rmnet_gro_downlink(gro_res);
 			} else {
 				netif_receive_skb(skb);
 			}

net/rmnet_data/rmnet_data_vnd.c

@@ -19,6 +19,7 @@
 #include <linux/rmnet_data.h>
 #include <linux/msm_rmnet.h>
 #include <linux/etherdevice.h>
+#include <linux/netdevice.h>
 #include <linux/if_arp.h>
 #include <linux/spinlock.h>
 #include <net/pkt_sched.h>
@@ -37,6 +38,9 @@ RMNET_LOG_MODULE(RMNET_DATA_LOGMASK_VND);
 #define RMNET_MAP_FLOW_NUM_TC_HANDLE 3
 #define RMNET_VND_UF_ACTION_ADD 0
 #define RMNET_VND_UF_ACTION_DEL 1
+#define RMNET_DATA_NAPI_WEIGHT 1
+#define RMNET_DATA_NAPI_WORK 0
+
 enum {
 	RMNET_VND_UPDATE_FLOW_OK,
 	RMNET_VND_UPDATE_FLOW_NO_ACTION,
@@ -58,7 +62,7 @@ struct rmnet_map_flow_mapping_s {
 struct rmnet_vnd_private_s {
 	uint32_t qos_version;
 	struct rmnet_logical_ep_conf_s local_ep;
-
+	struct napi_struct napi;
 	rwlock_t flow_map_lock;
 	struct list_head flow_head;
 	struct rmnet_map_flow_mapping_s root_flow;
@@ -503,6 +507,19 @@ static void rmnet_vnd_setup(struct net_device *dev)
 	INIT_LIST_HEAD(&dev_conf->flow_head);
 }
 
+/**
+ * rmnet_data_napi_poll() - NAPI poll function
+ * @napi:      NAPI struct
+ *
+ * Called by net_rx_action() when NAPI is scheduled. Since we have already
+ * queued packets to network stack, we just flush and return here.
+ */
+static int rmnet_data_napi_poll(struct napi_struct *napi, int budget)
+{
+	napi_complete(napi);
+	return RMNET_DATA_NAPI_WORK;
+}
+
 /* ***************** Exposed API ******************************************** */
 
 /**
@@ -557,6 +574,7 @@ int rmnet_vnd_create_dev(int id, struct net_device **new_device,
 	struct net_device *dev;
 	char dev_prefix[IFNAMSIZ];
 	int p, rc = 0;
+	struct napi_struct *n;
 
 	if (id < 0 || id >= RMNET_DATA_MAX_VND) {
 		*new_device = 0;
@@ -608,6 +626,10 @@ int rmnet_vnd_create_dev(int id, struct net_device **new_device,
 		*new_device = dev;
 	}
 
+	n = rmnet_vnd_get_napi(dev);
+	netif_napi_add(dev, n, rmnet_data_napi_poll, RMNET_DATA_NAPI_WEIGHT);
+	napi_enable(n);
+
 	LOGM("Registered device %s", dev->name);
 	return rc;
 }
@@ -651,6 +673,10 @@ int rmnet_vnd_free_dev(int id)
 	rtnl_unlock();
 
 	if (dev) {
+		struct napi_struct *n = rmnet_vnd_get_napi(dev);
+
+		napi_disable(n);
+		netif_napi_del(n);
 		unregister_netdev(dev);
 		free_netdev(dev);
 		return 0;
@@ -1091,3 +1117,15 @@ struct net_device *rmnet_vnd_get_by_id(int id)
 	}
 	return rmnet_devices[id];
 }
+
+/**
+ * rmnet_vnd_get_napi() - Get NAPI struct from the device
+ * @dev: Virtual network device
+ *
+ * Return:
+ *      - napi struct corresponding to the netdevice
+ */
+struct napi_struct *rmnet_vnd_get_napi(struct net_device *dev)
+{
+	return &(((struct rmnet_vnd_private_s *)netdev_priv(dev))->napi);
+}

net/rmnet_data/rmnet_data_vnd.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2014, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2013-2015, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -37,5 +37,6 @@ int rmnet_vnd_del_tc_flow(uint32_t id, uint32_t map_flow, uint32_t tc_flow);
 int rmnet_vnd_init(void);
 void rmnet_vnd_exit(void);
 struct net_device *rmnet_vnd_get_by_id(int id);
+struct napi_struct *rmnet_vnd_get_napi(struct net_device *dev);
 
 #endif /* _RMNET_DATA_VND_H_ */