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

The hardif 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

@@ -1218,7 +1218,7 @@ static bool batadv_iv_ogm_calc_tq(struct batadv_orig_node *orig_node,
 	inv_asym_penalty = BATADV_TQ_MAX_VALUE * neigh_rq_inv_cube;
 	inv_asym_penalty /= neigh_rq_max_cube;
 	tq_asym_penalty = BATADV_TQ_MAX_VALUE - inv_asym_penalty;
-	tq_iface_hop_penalty -= atomic_read(&if_incoming->hop_penalty);
+	tq_iface_hop_penalty -= READ_ONCE(if_incoming->hop_penalty);
 
 	/* penalize if the OGM is forwarded on the same interface. WiFi
 	 * interfaces and other half duplex devices suffer from throughput

net/batman-adv/bat_v.c

@@ -7,7 +7,6 @@
 #include "bat_v.h"
 #include "main.h"
 
-#include <linux/atomic.h>
 #include <linux/cache.h>
 #include <linux/compiler.h>
 #include <linux/errno.h>
@@ -813,8 +812,8 @@ void batadv_v_hardif_init(struct batadv_hard_iface *hard_iface)
 	/* enable link throughput auto-detection by setting the throughput
 	 * override to zero
 	 */
-	atomic_set(&hard_iface->bat_v.throughput_override, 0);
-	atomic_set(&hard_iface->bat_v.elp_interval, 500);
+	WRITE_ONCE(hard_iface->bat_v.throughput_override, 0);
+	WRITE_ONCE(hard_iface->bat_v.elp_interval, 500);
 
 	hard_iface->bat_v.aggr_len = 0;
 	skb_queue_head_init(&hard_iface->bat_v.aggr_list);

net/batman-adv/bat_v_elp.c

@@ -10,6 +10,7 @@
 #include <linux/atomic.h>
 #include <linux/bitops.h>
 #include <linux/byteorder/generic.h>
+#include <linux/compiler.h>
 #include <linux/container_of.h>
 #include <linux/errno.h>
 #include <linux/etherdevice.h>
@@ -62,7 +63,7 @@ static void batadv_v_elp_start_timer(struct batadv_hard_iface *hard_iface)
 {
 	unsigned int msecs;
 
-	msecs = atomic_read(&hard_iface->bat_v.elp_interval) - BATADV_JITTER;
+	msecs = READ_ONCE(hard_iface->bat_v.elp_interval) - BATADV_JITTER;
 	msecs += get_random_u32_below(2 * BATADV_JITTER);
 
 	queue_delayed_work(batadv_event_workqueue, &hard_iface->bat_v.elp_wq,
@@ -98,7 +99,7 @@ static bool batadv_v_elp_get_throughput(struct batadv_hardif_neigh_node *neigh,
 	/* if the user specified a customised value for this interface, then
 	 * return it directly
 	 */
-	throughput =  atomic_read(&hard_iface->bat_v.throughput_override);
+	throughput =  READ_ONCE(hard_iface->bat_v.throughput_override);
 	if (throughput != 0) {
 		*pthroughput = throughput;
 		return true;
@@ -324,7 +325,7 @@ static void batadv_v_elp_periodic_work(struct work_struct *work)
 
 	elp_packet = (struct batadv_elp_packet *)skb->data;
 	elp_packet->seqno = htonl(atomic_read(&hard_iface->bat_v.elp_seqno));
-	elp_interval = atomic_read(&hard_iface->bat_v.elp_interval);
+	elp_interval = READ_ONCE(hard_iface->bat_v.elp_interval);
 	elp_packet->elp_interval = htonl(elp_interval);
 
 	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,

net/batman-adv/bat_v_ogm.c

@@ -486,9 +486,9 @@ static u32 batadv_v_forward_penalty(struct batadv_priv *bat_priv,
 				    struct batadv_hard_iface *if_outgoing,
 				    u32 throughput)
 {
-	int if_hop_penalty = atomic_read(&if_incoming->hop_penalty);
-	int hop_penalty = READ_ONCE(bat_priv->hop_penalty);
-	int hop_penalty_max = BATADV_TQ_MAX_VALUE;
+	u32 if_hop_penalty = READ_ONCE(if_incoming->hop_penalty);
+	u32 hop_penalty = READ_ONCE(bat_priv->hop_penalty);
+	u32 hop_penalty_max = BATADV_TQ_MAX_VALUE;
 
 	/* Apply per hardif hop penalty */
 	throughput = throughput * (hop_penalty_max - if_hop_penalty) /

net/batman-adv/hard-interface.c

@@ -910,7 +910,7 @@ batadv_hardif_add_interface(struct net_device *net_dev)
 	if (batadv_is_wifi_hardif(hard_iface))
 		hard_iface->num_bcasts = BATADV_NUM_BCASTS_WIRELESS;
 
-	atomic_set(&hard_iface->hop_penalty, 0);
+	WRITE_ONCE(hard_iface->hop_penalty, 0);
 
 	batadv_v_hardif_init(hard_iface);
 

net/batman-adv/netlink.c

@@ -811,16 +811,16 @@ static int batadv_netlink_hardif_fill(struct sk_buff *msg,
 	}
 
 	if (nla_put_u8(msg, BATADV_ATTR_HOP_PENALTY,
-		       atomic_read(&hard_iface->hop_penalty)))
+		       READ_ONCE(hard_iface->hop_penalty)))
 		goto nla_put_failure;
 
 #ifdef CONFIG_BATMAN_ADV_BATMAN_V
 	if (nla_put_u32(msg, BATADV_ATTR_ELP_INTERVAL,
-			atomic_read(&hard_iface->bat_v.elp_interval)))
+			READ_ONCE(hard_iface->bat_v.elp_interval)))
 		goto nla_put_failure;
 
 	if (nla_put_u32(msg, BATADV_ATTR_THROUGHPUT_OVERRIDE,
-			atomic_read(&hard_iface->bat_v.throughput_override)))
+			READ_ONCE(hard_iface->bat_v.throughput_override)))
 		goto nla_put_failure;
 #endif /* CONFIG_BATMAN_ADV_BATMAN_V */
 
@@ -913,21 +913,21 @@ static int batadv_netlink_set_hardif(struct sk_buff *skb,
 	if (info->attrs[BATADV_ATTR_HOP_PENALTY]) {
 		attr = info->attrs[BATADV_ATTR_HOP_PENALTY];
 
-		atomic_set(&hard_iface->hop_penalty, nla_get_u8(attr));
+		WRITE_ONCE(hard_iface->hop_penalty, nla_get_u8(attr));
 	}
 
 #ifdef CONFIG_BATMAN_ADV_BATMAN_V
 
 	if (info->attrs[BATADV_ATTR_ELP_INTERVAL]) {
 		attr = info->attrs[BATADV_ATTR_ELP_INTERVAL];
 
-		atomic_set(&hard_iface->bat_v.elp_interval, nla_get_u32(attr));
+		WRITE_ONCE(hard_iface->bat_v.elp_interval, nla_get_u32(attr));
 	}
 
 	if (info->attrs[BATADV_ATTR_THROUGHPUT_OVERRIDE]) {
 		attr = info->attrs[BATADV_ATTR_THROUGHPUT_OVERRIDE];
 
-		atomic_set(&hard_iface->bat_v.throughput_override,
+		WRITE_ONCE(hard_iface->bat_v.throughput_override,
 			   nla_get_u32(attr));
 	}
 #endif /* CONFIG_BATMAN_ADV_BATMAN_V */

net/batman-adv/types.h

@@ -114,7 +114,7 @@ enum batadv_v_hard_iface_flags {
  */
 struct batadv_hard_iface_bat_v {
 	/** @elp_interval: time interval between two ELP transmissions */
-	atomic_t elp_interval;
+	u32 elp_interval;
 
 	/** @elp_seqno: current ELP sequence number */
 	atomic_t elp_seqno;
@@ -138,7 +138,7 @@ struct batadv_hard_iface_bat_v {
 	 * @throughput_override: throughput override to disable link
 	 *  auto-detection
 	 */
-	atomic_t throughput_override;
+	u32 throughput_override;
 
 	/** @flags: interface specific flags */
 	u8 flags;
@@ -236,7 +236,7 @@ struct batadv_hard_iface {
 	 * @hop_penalty: penalty which will be applied to the tq-field
 	 * of an OGM received via this interface
 	 */
-	atomic_t hop_penalty;
+	u8 hop_penalty;
 
 	/** @bat_iv: per hard-interface B.A.T.M.A.N. IV data */
 	struct batadv_hard_iface_bat_iv bat_iv;