mac80211: add separate last_ack variable

Instead of touching the rx_stats.last_rx from the status path, introduce
and use a status_stats.last_ack variable. This will make rx_stats.last_rx
indicate when the last frame was received, making it available for real
"last_rx" and statistics gathering; statistics, when done per-CPU, will
need to figure out which place was updated last for those items where the
"last" value is exposed.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 4f19505..ac73b9c 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -1094,10 +1094,12 @@
 	mutex_lock(&local->sta_mtx);
 
 	list_for_each_entry_safe(sta, tmp, &local->sta_list, list) {
+		unsigned long last_active = ieee80211_sta_last_active(sta);
+
 		if (sdata != sta->sdata)
 			continue;
 
-		if (time_after(jiffies, sta->rx_stats.last_rx + exp_time)) {
+		if (time_is_before_jiffies(last_active + exp_time)) {
 			sta_dbg(sta->sdata, "expiring inactive STA %pM\n",
 				sta->sta.addr);
 
@@ -2000,7 +2002,7 @@
 
 	sinfo->connected_time = ktime_get_seconds() - sta->last_connected;
 	sinfo->inactive_time =
-		jiffies_to_msecs(jiffies - sta->rx_stats.last_rx);
+		jiffies_to_msecs(jiffies - ieee80211_sta_last_active(sta));
 
 	if (!(sinfo->filled & (BIT(NL80211_STA_INFO_TX_BYTES64) |
 			       BIT(NL80211_STA_INFO_TX_BYTES)))) {
@@ -2186,3 +2188,10 @@
 		sinfo->expected_throughput = thr;
 	}
 }
+
+unsigned long ieee80211_sta_last_active(struct sta_info *sta)
+{
+	if (time_after(sta->rx_stats.last_rx, sta->status_stats.last_ack))
+		return sta->rx_stats.last_rx;
+	return sta->status_stats.last_ack;
+}