mac80211: optimise mixed AP/VLAN station removal

Teach sta_info_flush() to optionally also remove stations
from all VLANs associated with an AP interface to optimise
the station removal (in particular, synchronize_net().)

To not have to add the vlans argument throughout, do some
refactoring.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/cfg.c

@@ -1097,9 +1097,7 @@ static int ieee80211_stop_ap(struct wiphy *wiphy, struct net_device *dev)
 	if (old_probe_resp)
 		kfree_rcu(old_probe_resp, rcu_head);
 
-	list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
-		sta_info_flush(vlan);
-	sta_info_flush(sdata);
+	__sta_info_flush(sdata, true);
 	synchronize_net();
 	list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
 		ieee80211_free_keys(vlan);

net/mac80211/sta_info.c

@@ -960,7 +960,7 @@ void sta_info_stop(struct ieee80211_local *local)
 }
 
 
-int sta_info_flush(struct ieee80211_sub_if_data *sdata)
+int __sta_info_flush(struct ieee80211_sub_if_data *sdata, bool vlans)
 {
 	struct ieee80211_local *local = sdata->local;
 	struct sta_info *sta, *tmp;
@@ -969,9 +969,13 @@ int sta_info_flush(struct ieee80211_sub_if_data *sdata)
 
 	might_sleep();
 
+	WARN_ON(vlans && sdata->vif.type != NL80211_IFTYPE_AP);
+	WARN_ON(vlans && !sdata->bss);
+
 	mutex_lock(&local->sta_mtx);
 	list_for_each_entry_safe(sta, tmp, &local->sta_list, list) {
-		if (sdata == sta->sdata) {
+		if (sdata == sta->sdata ||
+		    (vlans && sdata->bss == sta->sdata->bss)) {
 			if (!WARN_ON(__sta_info_destroy_part1(sta)))
 				list_add(&sta->free_list, &free_list);
 			ret++;

net/mac80211/sta_info.h

@@ -613,8 +613,14 @@ void sta_info_stop(struct ieee80211_local *local);
  * Returns the number of removed STA entries.
  *
  * @sdata: sdata to remove all stations from
+ * @vlans: if the given interface is an AP interface, also flush VLANs
  */
-int sta_info_flush(struct ieee80211_sub_if_data *sdata);
+int __sta_info_flush(struct ieee80211_sub_if_data *sdata, bool vlans);
+
+static inline int sta_info_flush(struct ieee80211_sub_if_data *sdata)
+{
+	return __sta_info_flush(sdata, false);
+}
 
 void sta_set_rate_info_tx(struct sta_info *sta,
 			  const struct ieee80211_tx_rate *rate,