batman-adv: replace non-atomic meshif config fields with (READ|WRITE)_ONCE

The meshif configuration values are only accessed as plain loads/stores and
do not require full atomic_t semantics. Convert these fields to native
integer types and replace their users with READ_ONCE()/WRITE_ONCE() to
avoid load/store tearing.

Signed-off-by: Sven Eckelmann <sven@narfation.org>

Author: ecsv

net/batman-adv/bat_iv_ogm.c

@@ -13,6 +13,7 @@
 #include <linux/bug.h>
 #include <linux/byteorder/generic.h>
 #include <linux/cache.h>
+#include <linux/compiler.h>
 #include <linux/container_of.h>
 #include <linux/errno.h>
 #include <linux/etherdevice.h>
@@ -274,7 +275,7 @@ batadv_iv_ogm_emit_send_time(const struct batadv_priv *bat_priv)
 {
 	unsigned int msecs;
 
-	msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER;
+	msecs = READ_ONCE(bat_priv->orig_interval) - BATADV_JITTER;
 	msecs += get_random_u32_below(2 * BATADV_JITTER);
 
 	return jiffies + msecs_to_jiffies(msecs);
@@ -289,7 +290,7 @@ static unsigned long batadv_iv_ogm_fwd_send_time(void)
 /* apply hop penalty for a normal link */
 static u8 batadv_hop_penalty(u8 tq, const struct batadv_priv *bat_priv)
 {
-	int hop_penalty = atomic_read(&bat_priv->hop_penalty);
+	int hop_penalty = READ_ONCE(bat_priv->hop_penalty);
 	int new_tq;
 
 	new_tq = tq * (BATADV_TQ_MAX_VALUE - hop_penalty);
@@ -555,7 +556,7 @@ static bool batadv_iv_ogm_aggregate_new(const unsigned char *packet_buff,
 	unsigned int skb_size;
 	atomic_t *queue_left = own_packet ? NULL : &bat_priv->batman_queue_left;
 
-	if (atomic_read(&bat_priv->aggregated_ogms))
+	if (READ_ONCE(bat_priv->aggregated_ogms))
 		skb_size = max_t(unsigned int, BATADV_MAX_AGGREGATION_BYTES,
 				 packet_len);
 	else
@@ -641,15 +642,18 @@ static bool batadv_iv_ogm_queue_add(struct batadv_priv *bat_priv,
 	struct batadv_ogm_packet *batadv_ogm_packet;
 	bool direct_link;
 	unsigned long max_aggregation_jiffies;
+	bool aggregated_ogms;
 
 	batadv_ogm_packet = (struct batadv_ogm_packet *)packet_buff;
 	direct_link = !!(batadv_ogm_packet->flags & BATADV_DIRECTLINK);
 	max_aggregation_jiffies = msecs_to_jiffies(BATADV_MAX_AGGREGATION_MS);
 
 	/* find position for the packet in the forward queue */
 	spin_lock_bh(&bat_priv->forw_bat_list_lock);
+	aggregated_ogms = READ_ONCE(bat_priv->aggregated_ogms);
+
 	/* own packets are not to be aggregated */
-	if (atomic_read(&bat_priv->aggregated_ogms) && !own_packet) {
+	if (aggregated_ogms && !own_packet) {
 		hlist_for_each_entry(forw_packet_pos,
 				     &bat_priv->forw_bat_list, list) {
 			if (batadv_iv_ogm_can_aggregate(batadv_ogm_packet,
@@ -675,7 +679,7 @@ static bool batadv_iv_ogm_queue_add(struct batadv_priv *bat_priv,
 		 * we hold it back for a while, so that it might be aggregated
 		 * later on
 		 */
-		if (!own_packet && atomic_read(&bat_priv->aggregated_ogms))
+		if (!own_packet && aggregated_ogms)
 			send_time += max_aggregation_jiffies;
 
 		return batadv_iv_ogm_aggregate_new(packet_buff, packet_len,
@@ -888,7 +892,7 @@ static void batadv_iv_ogm_schedule_buff(struct batadv_hard_iface *hard_iface)
 		 */
 		queue_delayed_work(batadv_event_workqueue,
 				   &hard_iface->bat_iv.reschedule_work,
-				   msecs_to_jiffies(atomic_read(&bat_priv->orig_interval)));
+				   msecs_to_jiffies(READ_ONCE(bat_priv->orig_interval)));
 	}
 
 	batadv_hardif_put(primary_if);
@@ -2321,7 +2325,7 @@ static void batadv_iv_iface_enabled(struct batadv_hard_iface *hard_iface)
 static void batadv_iv_init_sel_class(struct batadv_priv *bat_priv)
 {
 	/* set default TQ difference threshold to 20 */
-	atomic_set(&bat_priv->gw.sel_class, 20);
+	WRITE_ONCE(bat_priv->gw.sel_class, 20);
 }
 
 static struct batadv_gw_node *
@@ -2353,7 +2357,7 @@ batadv_iv_gw_get_best_gw_node(struct batadv_priv *bat_priv)
 
 		tq_avg = router_ifinfo->bat_iv.tq_avg;
 
-		switch (atomic_read(&bat_priv->gw.sel_class)) {
+		switch (READ_ONCE(bat_priv->gw.sel_class)) {
 		case 1: /* fast connection */
 			tmp_gw_factor = tq_avg * tq_avg;
 			tmp_gw_factor *= gw_node->bandwidth_down;
@@ -2407,13 +2411,14 @@ static bool batadv_iv_gw_is_eligible(struct batadv_priv *bat_priv,
 {
 	struct batadv_neigh_ifinfo *router_orig_ifinfo = NULL;
 	struct batadv_neigh_ifinfo *router_gw_ifinfo = NULL;
+	u32 sel_class = READ_ONCE(bat_priv->gw.sel_class);
 	struct batadv_neigh_node *router_gw = NULL;
 	struct batadv_neigh_node *router_orig = NULL;
 	u8 gw_tq_avg, orig_tq_avg;
 	bool ret = false;
 
 	/* dynamic re-election is performed only on fast or late switch */
-	if (atomic_read(&bat_priv->gw.sel_class) <= 2)
+	if (sel_class <= 2)
 		return false;
 
 	router_gw = batadv_orig_router_get(curr_gw_orig, BATADV_IF_DEFAULT);
@@ -2448,8 +2453,7 @@ static bool batadv_iv_gw_is_eligible(struct batadv_priv *bat_priv,
 	/* if the routing class is greater than 3 the value tells us how much
 	 * greater the TQ value of the new gateway must be
 	 */
-	if ((atomic_read(&bat_priv->gw.sel_class) > 3) &&
-	    (orig_tq_avg - gw_tq_avg < atomic_read(&bat_priv->gw.sel_class)))
+	if (sel_class > 3 && orig_tq_avg - gw_tq_avg < sel_class)
 		goto out;
 
 	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,

net/batman-adv/bat_v.c

@@ -9,6 +9,7 @@
 
 #include <linux/atomic.h>
 #include <linux/cache.h>
+#include <linux/compiler.h>
 #include <linux/errno.h>
 #include <linux/if_ether.h>
 #include <linux/init.h>
@@ -505,7 +506,7 @@ static bool batadv_v_neigh_is_sob(struct batadv_neigh_node *neigh1,
 static void batadv_v_init_sel_class(struct batadv_priv *bat_priv)
 {
 	/* set default throughput difference threshold to 5Mbps */
-	atomic_set(&bat_priv->gw.sel_class, 50);
+	WRITE_ONCE(bat_priv->gw.sel_class, 50);
 }
 
 /**
@@ -602,7 +603,7 @@ static bool batadv_v_gw_is_eligible(struct batadv_priv *bat_priv,
 	u32 gw_throughput, orig_throughput, threshold;
 	bool ret = false;
 
-	threshold = atomic_read(&bat_priv->gw.sel_class);
+	threshold = READ_ONCE(bat_priv->gw.sel_class);
 
 	curr_gw = batadv_gw_node_get(bat_priv, curr_gw_orig);
 	if (!curr_gw) {

net/batman-adv/bat_v_ogm.c

@@ -10,6 +10,7 @@
 #include <linux/atomic.h>
 #include <linux/bug.h>
 #include <linux/byteorder/generic.h>
+#include <linux/compiler.h>
 #include <linux/container_of.h>
 #include <linux/errno.h>
 #include <linux/etherdevice.h>
@@ -106,7 +107,7 @@ static void batadv_v_ogm_start_timer(struct batadv_priv *bat_priv)
 	if (delayed_work_pending(&bat_priv->bat_v.ogm_wq))
 		return;
 
-	msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER;
+	msecs = READ_ONCE(bat_priv->orig_interval) - BATADV_JITTER;
 	msecs += get_random_u32_below(2 * BATADV_JITTER);
 	queue_delayed_work(batadv_event_workqueue, &bat_priv->bat_v.ogm_wq,
 			   msecs_to_jiffies(msecs));
@@ -247,7 +248,7 @@ static void batadv_v_ogm_queue_on_if(struct batadv_priv *bat_priv,
 		return;
 	}
 
-	if (!atomic_read(&bat_priv->aggregated_ogms)) {
+	if (!READ_ONCE(bat_priv->aggregated_ogms)) {
 		batadv_v_ogm_send_to_if(bat_priv, skb, hard_iface);
 		return;
 	}
@@ -486,7 +487,7 @@ static u32 batadv_v_forward_penalty(struct batadv_priv *bat_priv,
 				    u32 throughput)
 {
 	int if_hop_penalty = atomic_read(&if_incoming->hop_penalty);
-	int hop_penalty = atomic_read(&bat_priv->hop_penalty);
+	int hop_penalty = READ_ONCE(bat_priv->hop_penalty);
 	int hop_penalty_max = BATADV_TQ_MAX_VALUE;
 
 	/* Apply per hardif hop penalty */

net/batman-adv/bridge_loop_avoidance.c

@@ -1380,7 +1380,7 @@ void batadv_bla_update_orig_address(struct batadv_priv *bat_priv,
 	bat_priv->bla.claim_dest.group = group;
 
 	/* purge everything when bridge loop avoidance is turned off */
-	if (!atomic_read(&bat_priv->bridge_loop_avoidance))
+	if (!READ_ONCE(bat_priv->bridge_loop_avoidance))
 		oldif = NULL;
 
 	if (!oldif) {
@@ -1484,7 +1484,7 @@ static void batadv_bla_periodic_work(struct work_struct *work)
 	batadv_bla_purge_claims(bat_priv, primary_if, 0);
 	batadv_bla_purge_backbone_gw(bat_priv, 0);
 
-	if (!atomic_read(&bat_priv->bridge_loop_avoidance))
+	if (!READ_ONCE(bat_priv->bridge_loop_avoidance))
 		goto out;
 
 	if (atomic_dec_and_test(&bat_priv->bla.loopdetect_next)) {
@@ -1783,7 +1783,7 @@ bool batadv_bla_is_backbone_gw_orig(struct batadv_priv *bat_priv, u8 *orig,
 	struct batadv_bla_backbone_gw *backbone_gw;
 	int i;
 
-	if (!atomic_read(&bat_priv->bridge_loop_avoidance))
+	if (!READ_ONCE(bat_priv->bridge_loop_avoidance))
 		return false;
 
 	if (!hash)
@@ -1821,7 +1821,7 @@ bool batadv_bla_is_backbone_gw(struct sk_buff *skb,
 	struct batadv_bla_backbone_gw *backbone_gw;
 	unsigned short vid;
 
-	if (!atomic_read(&orig_node->bat_priv->bridge_loop_avoidance))
+	if (!READ_ONCE(orig_node->bat_priv->bridge_loop_avoidance))
 		return false;
 
 	/* first, find out the vid. */
@@ -1953,7 +1953,7 @@ bool batadv_bla_rx(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	if (!primary_if)
 		goto handled;
 
-	if (!atomic_read(&bat_priv->bridge_loop_avoidance))
+	if (!READ_ONCE(bat_priv->bridge_loop_avoidance))
 		goto allow;
 
 	if (batadv_bla_loopdetect_check(bat_priv, skb, primary_if, vid))
@@ -2085,7 +2085,7 @@ bool batadv_bla_tx(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	if (!primary_if)
 		goto out;
 
-	if (!atomic_read(&bat_priv->bridge_loop_avoidance))
+	if (!READ_ONCE(bat_priv->bridge_loop_avoidance))
 		goto allow;
 
 	if (batadv_bla_process_claim(bat_priv, primary_if, skb))
@@ -2505,7 +2505,7 @@ bool batadv_bla_check_claim(struct batadv_priv *bat_priv,
 	struct batadv_hard_iface *primary_if = NULL;
 	bool ret = true;
 
-	if (!atomic_read(&bat_priv->bridge_loop_avoidance))
+	if (!READ_ONCE(bat_priv->bridge_loop_avoidance))
 		return ret;
 
 	primary_if = batadv_primary_if_get_selected(bat_priv);

net/batman-adv/distributed-arp-table.c

@@ -743,7 +743,7 @@ static void batadv_dat_tvlv_container_update(struct batadv_priv *bat_priv)
 {
 	char dat_mode;
 
-	dat_mode = atomic_read(&bat_priv->distributed_arp_table);
+	dat_mode = READ_ONCE(bat_priv->distributed_arp_table);
 
 	switch (dat_mode) {
 	case 0:
@@ -1139,7 +1139,7 @@ bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
 	int hdr_size = 0;
 	unsigned short vid;
 
-	if (!atomic_read(&bat_priv->distributed_arp_table))
+	if (!READ_ONCE(bat_priv->distributed_arp_table))
 		goto out;
 
 	vid = batadv_dat_get_vid(skb, &hdr_size);
@@ -1234,7 +1234,7 @@ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
 	unsigned short vid;
 	int err;
 
-	if (!atomic_read(&bat_priv->distributed_arp_table))
+	if (!READ_ONCE(bat_priv->distributed_arp_table))
 		goto out;
 
 	vid = batadv_dat_get_vid(skb, &hdr_size);
@@ -1296,7 +1296,7 @@ void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv,
 	int hdr_size = 0;
 	unsigned short vid;
 
-	if (!atomic_read(&bat_priv->distributed_arp_table))
+	if (!READ_ONCE(bat_priv->distributed_arp_table))
 		return;
 
 	vid = batadv_dat_get_vid(skb, &hdr_size);
@@ -1344,7 +1344,7 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
 	bool dropped = false;
 	unsigned short vid;
 
-	if (!atomic_read(&bat_priv->distributed_arp_table))
+	if (!READ_ONCE(bat_priv->distributed_arp_table))
 		goto out;
 
 	vid = batadv_dat_get_vid(skb, &hdr_size);
@@ -1714,7 +1714,7 @@ void batadv_dat_snoop_outgoing_dhcp_ack(struct batadv_priv *bat_priv,
 	u8 chaddr[BATADV_DHCP_CHADDR_LEN];
 	__be32 ip_src, yiaddr;
 
-	if (!atomic_read(&bat_priv->distributed_arp_table))
+	if (!READ_ONCE(bat_priv->distributed_arp_table))
 		return;
 
 	if (!batadv_dat_check_dhcp_ack(skb, proto, &ip_src, chaddr, &yiaddr))
@@ -1744,7 +1744,7 @@ void batadv_dat_snoop_incoming_dhcp_ack(struct batadv_priv *bat_priv,
 	__be16 proto;
 	u8 *hw_src;
 
-	if (!atomic_read(&bat_priv->distributed_arp_table))
+	if (!READ_ONCE(bat_priv->distributed_arp_table))
 		return;
 
 	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
@@ -1789,7 +1789,7 @@ bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv,
 	int hdr_size = sizeof(struct batadv_bcast_packet);
 	unsigned short vid;
 
-	if (!atomic_read(&bat_priv->distributed_arp_table))
+	if (!READ_ONCE(bat_priv->distributed_arp_table))
 		goto out;
 
 	/* If this packet is an ARP_REQUEST and the node already has the

net/batman-adv/gateway_client.c

@@ -171,7 +171,7 @@ void batadv_gw_check_client_stop(struct batadv_priv *bat_priv)
 {
 	struct batadv_gw_node *curr_gw;
 
-	if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
+	if (READ_ONCE(bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
 		return;
 
 	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
@@ -203,7 +203,7 @@ void batadv_gw_election(struct batadv_priv *bat_priv)
 	struct batadv_neigh_ifinfo *router_ifinfo = NULL;
 	char gw_addr[18] = { '\0' };
 
-	if (atomic_read(&bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
+	if (READ_ONCE(bat_priv->gw.mode) != BATADV_GW_MODE_CLIENT)
 		goto out;
 
 	if (!bat_priv->algo_ops->gw.get_best_gw_node)
@@ -703,7 +703,7 @@ bool batadv_gw_out_of_range(struct batadv_priv *bat_priv,
 	if (!gw_node)
 		goto out;
 
-	switch (atomic_read(&bat_priv->gw.mode)) {
+	switch (READ_ONCE(bat_priv->gw.mode)) {
 	case BATADV_GW_MODE_SERVER:
 		/* If we are a GW then we are our best GW. We can artificially
 		 * set the tq towards ourself as the maximum value

net/batman-adv/gateway_common.c

@@ -7,8 +7,8 @@
 #include "gateway_common.h"
 #include "main.h"
 
-#include <linux/atomic.h>
 #include <linux/byteorder/generic.h>
+#include <linux/compiler.h>
 #include <linux/stddef.h>
 #include <linux/types.h>
 #include <uapi/linux/batadv_packet.h>
@@ -25,19 +25,19 @@
 void batadv_gw_tvlv_container_update(struct batadv_priv *bat_priv)
 {
 	struct batadv_tvlv_gateway_data gw;
+	enum batadv_gw_modes gw_mode;
 	u32 down, up;
-	char gw_mode;
 
-	gw_mode = atomic_read(&bat_priv->gw.mode);
+	gw_mode = READ_ONCE(bat_priv->gw.mode);
 
 	switch (gw_mode) {
 	case BATADV_GW_MODE_OFF:
 	case BATADV_GW_MODE_CLIENT:
 		batadv_tvlv_container_unregister(bat_priv, BATADV_TVLV_GW, 1);
 		break;
 	case BATADV_GW_MODE_SERVER:
-		down = atomic_read(&bat_priv->gw.bandwidth_down);
-		up = atomic_read(&bat_priv->gw.bandwidth_up);
+		down = READ_ONCE(bat_priv->gw.bandwidth_down);
+		up = READ_ONCE(bat_priv->gw.bandwidth_up);
 		gw.bandwidth_down = htonl(down);
 		gw.bandwidth_up = htonl(up);
 		batadv_tvlv_container_register(bat_priv, BATADV_TVLV_GW, 1,
@@ -83,7 +83,7 @@ static void batadv_gw_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
 
 	/* restart gateway selection */
 	if (gateway.bandwidth_down != 0 &&
-	    atomic_read(&bat_priv->gw.mode) == BATADV_GW_MODE_CLIENT)
+	    READ_ONCE(bat_priv->gw.mode) == BATADV_GW_MODE_CLIENT)
 		batadv_gw_check_election(bat_priv, orig);
 }
 
@@ -96,7 +96,7 @@ void batadv_gw_init(struct batadv_priv *bat_priv)
 	if (bat_priv->algo_ops->gw.init_sel_class)
 		bat_priv->algo_ops->gw.init_sel_class(bat_priv);
 	else
-		atomic_set(&bat_priv->gw.sel_class, 1);
+		WRITE_ONCE(bat_priv->gw.sel_class, 1);
 
 	batadv_tvlv_handler_register(bat_priv, batadv_gw_tvlv_ogm_handler_v1,
 				     NULL, NULL, BATADV_TVLV_GW, 1,