wifi: mac80211: use wiphy locked debugfs helpers for agg_status

The read is currently with RCU and the write can deadlock,
convert both for the sake of illustration.

Make mac80211 depend on cfg80211 debugfs to get the helpers,
but mac80211 debugfs without it does nothing anyway. This
also required some adjustments in ath9k.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/ath/ath9k/Kconfig

@@ -57,8 +57,7 @@ config ATH9K_AHB
 
 config ATH9K_DEBUGFS
 	bool "Atheros ath9k debugging"
-	depends on ATH9K && DEBUG_FS
-	select MAC80211_DEBUGFS
+	depends on ATH9K && DEBUG_FS && MAC80211_DEBUGFS
 	select ATH9K_COMMON_DEBUG
 	help
 	  Say Y, if you need access to ath9k's statistics for
@@ -70,7 +69,6 @@ config ATH9K_DEBUGFS
 config ATH9K_STATION_STATISTICS
 	bool "Detailed station statistics"
 	depends on ATH9K && ATH9K_DEBUGFS && DEBUG_FS
-	select MAC80211_DEBUGFS
 	default n
 	help
 	  This option enables detailed statistics for association stations.

net/mac80211/Kconfig

@@ -88,7 +88,7 @@ config MAC80211_LEDS
 
 config MAC80211_DEBUGFS
 	bool "Export mac80211 internals in DebugFS"
-	depends on MAC80211 && DEBUG_FS
+	depends on MAC80211 && CFG80211_DEBUGFS
 	help
 	  Select this to see extensive information about
 	  the internal state of mac80211 in debugfs.

net/mac80211/debugfs_sta.c

@@ -312,23 +312,14 @@ static ssize_t sta_aql_write(struct file *file, const char __user *userbuf,
 STA_OPS_RW(aql);
 
 
-static ssize_t sta_agg_status_read(struct file *file, char __user *userbuf,
-					size_t count, loff_t *ppos)
+static ssize_t sta_agg_status_do_read(struct wiphy *wiphy, struct file *file,
+				      char *buf, size_t bufsz, void *data)
 {
-	char *buf, *p;
-	ssize_t bufsz = 71 + IEEE80211_NUM_TIDS * 40;
+	struct sta_info *sta = data;
+	char *p = buf;
 	int i;
-	struct sta_info *sta = file->private_data;
 	struct tid_ampdu_rx *tid_rx;
 	struct tid_ampdu_tx *tid_tx;
-	ssize_t ret;
-
-	buf = kzalloc(bufsz, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-	p = buf;
-
-	rcu_read_lock();
 
 	p += scnprintf(p, bufsz + buf - p, "next dialog_token: %#02x\n",
 			sta->ampdu_mlme.dialog_token_allocator + 1);
@@ -338,8 +329,8 @@ static ssize_t sta_agg_status_read(struct file *file, char __user *userbuf,
 	for (i = 0; i < IEEE80211_NUM_TIDS; i++) {
 		bool tid_rx_valid;
 
-		tid_rx = rcu_dereference(sta->ampdu_mlme.tid_rx[i]);
-		tid_tx = rcu_dereference(sta->ampdu_mlme.tid_tx[i]);
+		tid_rx = wiphy_dereference(wiphy, sta->ampdu_mlme.tid_rx[i]);
+		tid_tx = wiphy_dereference(wiphy, sta->ampdu_mlme.tid_tx[i]);
 		tid_rx_valid = test_bit(i, sta->ampdu_mlme.agg_session_valid);
 
 		p += scnprintf(p, bufsz + buf - p, "%02d", i);
@@ -358,31 +349,39 @@ static ssize_t sta_agg_status_read(struct file *file, char __user *userbuf,
 				tid_tx ? skb_queue_len(&tid_tx->pending) : 0);
 		p += scnprintf(p, bufsz + buf - p, "\n");
 	}
-	rcu_read_unlock();
 
-	ret = simple_read_from_buffer(userbuf, count, ppos, buf, p - buf);
-	kfree(buf);
-	return ret;
+	return p - buf;
 }
 
-static ssize_t sta_agg_status_write(struct file *file, const char __user *userbuf,
+static ssize_t sta_agg_status_read(struct file *file, char __user *userbuf,
 				   size_t count, loff_t *ppos)
 {
-	char _buf[25] = {}, *buf = _buf;
 	struct sta_info *sta = file->private_data;
+	struct wiphy *wiphy = sta->local->hw.wiphy;
+	size_t bufsz = 71 + IEEE80211_NUM_TIDS * 40;
+	char *buf = kmalloc(bufsz, GFP_KERNEL);
+	ssize_t ret;
+
+	if (!buf)
+		return -ENOMEM;
+
+	ret = wiphy_locked_debugfs_read(wiphy, file, buf, bufsz,
+					userbuf, count, ppos,
+					sta_agg_status_do_read, sta);
+	kfree(buf);
+
+	return ret;
+}
+
+static ssize_t sta_agg_status_do_write(struct wiphy *wiphy, struct file *file,
+				       char *buf, size_t count, void *data)
+{
+	struct sta_info *sta = data;
 	bool start, tx;
 	unsigned long tid;
-	char *pos;
+	char *pos = buf;
 	int ret, timeout = 5000;
 
-	if (count > sizeof(_buf))
-		return -EINVAL;
-
-	if (copy_from_user(buf, userbuf, count))
-		return -EFAULT;
-
-	buf[sizeof(_buf) - 1] = '\0';
-	pos = buf;
 	buf = strsep(&pos, " ");
 	if (!buf)
 		return -EINVAL;
@@ -420,7 +419,6 @@ static ssize_t sta_agg_status_write(struct file *file, const char __user *userbu
 	if (ret || tid >= IEEE80211_NUM_TIDS)
 		return -EINVAL;
 
-	wiphy_lock(sta->local->hw.wiphy);
 	if (tx) {
 		if (start)
 			ret = ieee80211_start_tx_ba_session(&sta->sta, tid,
@@ -432,10 +430,22 @@ static ssize_t sta_agg_status_write(struct file *file, const char __user *userbu
 					       3, true);
 		ret = 0;
 	}
-	wiphy_unlock(sta->local->hw.wiphy);
 
 	return ret ?: count;
 }
+
+static ssize_t sta_agg_status_write(struct file *file,
+				    const char __user *userbuf,
+				    size_t count, loff_t *ppos)
+{
+	struct sta_info *sta = file->private_data;
+	struct wiphy *wiphy = sta->local->hw.wiphy;
+	char _buf[26];
+
+	return wiphy_locked_debugfs_write(wiphy, file, _buf, sizeof(_buf),
+					  userbuf, count,
+					  sta_agg_status_do_write, sta);
+}
 STA_OPS_RW(agg_status);
 
 /* link sta attributes */