mac80211: use RCU_INIT_POINTER

rcu_assign_pointer() ensures that the initialization of a structure is
carried out before storing a pointer to that structure. However, in the
case that NULL is assigned there's no structure to initialize so using
RCU_INIT_POINTER instead is safe and more efficient.

Signed-off-by: Monam Agarwal <monamagarwal123@gmail.com>
[squash eight tiny patches, rewrite commit log]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -1566,7 +1566,7 @@ static int ieee80211_change_station(struct wiphy *wiphy,
 
 		if (sta->sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
 		    sta->sdata->u.vlan.sta) {
-			rcu_assign_pointer(sta->sdata->u.vlan.sta, NULL);
+			RCU_INIT_POINTER(sta->sdata->u.vlan.sta, NULL);
 			prev_4addr = true;
 		}
 

net/mac80211/chan.c

@@ -392,7 +392,7 @@ static void ieee80211_unassign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
 	lockdep_assert_held(&local->chanctx_mtx);
 
 	ctx->refcount--;
-	rcu_assign_pointer(sdata->vif.chanctx_conf, NULL);
+	RCU_INIT_POINTER(sdata->vif.chanctx_conf, NULL);
 
 	sdata->vif.bss_conf.idle = true;
 

net/mac80211/debugfs.c

@@ -128,7 +128,7 @@ static ssize_t sta_tx_latency_stat_write(struct file *file,
 	if (!strcmp(buf, TX_LATENCY_DISABLED)) {
 		if (!tx_latency)
 			goto unlock;
-		rcu_assign_pointer(local->tx_latency, NULL);
+		RCU_INIT_POINTER(local->tx_latency, NULL);
 		synchronize_rcu();
 		kfree(tx_latency);
 		goto unlock;

net/mac80211/ibss.c

@@ -253,7 +253,7 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 
 	presp = rcu_dereference_protected(ifibss->presp,
 					  lockdep_is_held(&sdata->wdev.mtx));
-	rcu_assign_pointer(ifibss->presp, NULL);
+	RCU_INIT_POINTER(ifibss->presp, NULL);
 	if (presp)
 		kfree_rcu(presp, rcu_head);
 

net/mac80211/iface.c

@@ -423,7 +423,7 @@ int ieee80211_add_virtual_monitor(struct ieee80211_local *local)
 	mutex_unlock(&local->mtx);
 	if (ret) {
 		mutex_lock(&local->iflist_mtx);
-		rcu_assign_pointer(local->monitor_sdata, NULL);
+		RCU_INIT_POINTER(local->monitor_sdata, NULL);
 		mutex_unlock(&local->iflist_mtx);
 		synchronize_net();
 		drv_remove_interface(local, sdata);
@@ -452,7 +452,7 @@ void ieee80211_del_virtual_monitor(struct ieee80211_local *local)
 		return;
 	}
 
-	rcu_assign_pointer(local->monitor_sdata, NULL);
+	RCU_INIT_POINTER(local->monitor_sdata, NULL);
 	mutex_unlock(&local->iflist_mtx);
 
 	synchronize_net();
@@ -876,7 +876,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 	switch (sdata->vif.type) {
 	case NL80211_IFTYPE_AP_VLAN:
 		list_del(&sdata->u.vlan.list);
-		rcu_assign_pointer(sdata->vif.chanctx_conf, NULL);
+		RCU_INIT_POINTER(sdata->vif.chanctx_conf, NULL);
 		/* no need to tell driver */
 		break;
 	case NL80211_IFTYPE_MONITOR:
@@ -895,7 +895,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 		break;
 	case NL80211_IFTYPE_P2P_DEVICE:
 		/* relies on synchronize_rcu() below */
-		rcu_assign_pointer(local->p2p_sdata, NULL);
+		RCU_INIT_POINTER(local->p2p_sdata, NULL);
 		/* fall through */
 	default:
 		cancel_work_sync(&sdata->work);

net/mac80211/mesh.c

@@ -829,7 +829,7 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
 	ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON_ENABLED);
 	bcn = rcu_dereference_protected(ifmsh->beacon,
 					lockdep_is_held(&sdata->wdev.mtx));
-	rcu_assign_pointer(ifmsh->beacon, NULL);
+	RCU_INIT_POINTER(ifmsh->beacon, NULL);
 	kfree_rcu(bcn, rcu_head);
 
 	/* flush STAs and mpaths on this iface */
@@ -1068,7 +1068,7 @@ int ieee80211_mesh_finish_csa(struct ieee80211_sub_if_data *sdata)
 
 	/* Remove the CSA and MCSP elements from the beacon */
 	tmp_csa_settings = rcu_dereference(ifmsh->csa);
-	rcu_assign_pointer(ifmsh->csa, NULL);
+	RCU_INIT_POINTER(ifmsh->csa, NULL);
 	if (tmp_csa_settings)
 		kfree_rcu(tmp_csa_settings, rcu_head);
 	ret = ieee80211_mesh_rebuild_beacon(sdata);
@@ -1102,7 +1102,7 @@ int ieee80211_mesh_csa_beacon(struct ieee80211_sub_if_data *sdata,
 	ret = ieee80211_mesh_rebuild_beacon(sdata);
 	if (ret) {
 		tmp_csa_settings = rcu_dereference(ifmsh->csa);
-		rcu_assign_pointer(ifmsh->csa, NULL);
+		RCU_INIT_POINTER(ifmsh->csa, NULL);
 		kfree_rcu(tmp_csa_settings, rcu_head);
 		return ret;
 	}

net/mac80211/scan.c

@@ -309,7 +309,7 @@ static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
 	if (local->scan_req != local->int_scan_req)
 		cfg80211_scan_done(local->scan_req, aborted);
 	local->scan_req = NULL;
-	rcu_assign_pointer(local->scan_sdata, NULL);
+	RCU_INIT_POINTER(local->scan_sdata, NULL);
 
 	local->scanning = 0;
 	local->scan_chandef.chan = NULL;
@@ -559,7 +559,7 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
 		ieee80211_recalc_idle(local);
 
 		local->scan_req = NULL;
-		rcu_assign_pointer(local->scan_sdata, NULL);
+		RCU_INIT_POINTER(local->scan_sdata, NULL);
 	}
 
 	return rc;
@@ -773,7 +773,7 @@ void ieee80211_scan_work(struct work_struct *work)
 		int rc;
 
 		local->scan_req = NULL;
-		rcu_assign_pointer(local->scan_sdata, NULL);
+		RCU_INIT_POINTER(local->scan_sdata, NULL);
 
 		rc = __ieee80211_start_scan(sdata, req);
 		if (rc) {
@@ -1014,7 +1014,7 @@ out_free:
 
 	if (ret) {
 		/* Clean in case of failure after HW restart or upon resume. */
-		rcu_assign_pointer(local->sched_scan_sdata, NULL);
+		RCU_INIT_POINTER(local->sched_scan_sdata, NULL);
 		local->sched_scan_req = NULL;
 	}
 
@@ -1089,7 +1089,7 @@ void ieee80211_sched_scan_stopped_work(struct work_struct *work)
 		return;
 	}
 
-	rcu_assign_pointer(local->sched_scan_sdata, NULL);
+	RCU_INIT_POINTER(local->sched_scan_sdata, NULL);
 
 	/* If sched scan was aborted by the driver. */
 	local->sched_scan_req = NULL;

net/mac80211/util.c

@@ -1546,7 +1546,7 @@ int ieee80211_reconfig(struct ieee80211_local *local)
 		WARN_ON(local->resuming);
 		res = drv_add_interface(local, sdata);
 		if (WARN_ON(res)) {
-			rcu_assign_pointer(local->monitor_sdata, NULL);
+			RCU_INIT_POINTER(local->monitor_sdata, NULL);
 			synchronize_net();
 			kfree(sdata);
 		}