[PATCH v1 wl-next 3/3] wifi: wext: Don't iterate all netns in wireless_nlevent_flush().

[Kuniyuki Iwashima <kuniyu@amazon.com>]

Commit 8bf862739a77 ("wext: fix message delay/ordering") introduced
wext_netdev_notifier_call() to avoid message delay and out-of-order.

The notifier calls wireless_nlevent_flush(), which iterates all netns.

The problem is that this happens for any event and netdev, even if
the host does not have a wext device.

This is too noisy, especially on a host with thousands of netns as
reported by Alexandre Ferrieux.

Given that the wext event queue was implemented in struct net,
wireless_nlevent_flush() does not need to iterate all netns.

Let's avoid unnecessary netns iteration in wireless_nlevent_flush().

Reported-by: Alexandre Ferrieux <alexandre.ferrieux@gmail.com>
Closes: https://lore.kernel.org/netdev/CAKYWH0Ti3=4GeeuVyWKJ9LyTuRnf3Wy9GKg4Jb7tdeaT39qADA@mail.gmail.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/iw_handler.h |  4 ++--
 net/wireless/core.c      |  2 +-
 net/wireless/wext-core.c | 25 +++++++++++++------------
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/include/net/iw_handler.h b/include/net/iw_handler.h
index b80e474cb0aa..e6acff086d39 100644
--- a/include/net/iw_handler.h
+++ b/include/net/iw_handler.h
@@ -412,9 +412,9 @@ void wireless_send_event(struct net_device *dev, unsigned int cmd,
 			 union iwreq_data *wrqu, const char *extra);
 #ifdef CONFIG_WEXT_CORE
 /* flush all previous wext events - if work is done from netdev notifiers */
-void wireless_nlevent_flush(void);
+void wireless_nlevent_flush(struct net *net);
 #else
-static inline void wireless_nlevent_flush(void) {}
+static inline void wireless_nlevent_flush(struct net *net) {}
 #endif
 
 /* We may need a function to send a stream of events to user space.
diff --git a/net/wireless/core.c b/net/wireless/core.c
index 4c8d8f167409..a864ec889de3 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -1629,7 +1629,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 		return NOTIFY_DONE;
 	}
 
-	wireless_nlevent_flush();
+	wireless_nlevent_flush(dev_net(dev));
 
 	return NOTIFY_OK;
 }
diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c
index 4d7699135f46..28033211c9e3 100644
--- a/net/wireless/wext-core.c
+++ b/net/wireless/wext-core.c
@@ -345,6 +345,7 @@ static const int compat_event_type_size[] = {
 /* IW event code */
 
 struct wext_net {
+	struct net *net;
 	struct sk_buff_head nlevents;
 	struct work_struct nlevent_work;
 };
@@ -356,26 +357,22 @@ static struct wext_net *wext_net(struct net *net)
 	return net_generic(net, wext_net_id);
 }
 
-void wireless_nlevent_flush(void)
+void wireless_nlevent_flush(struct net *net)
 {
+	struct wext_net *wnet = wext_net(net);
 	struct sk_buff *skb;
-	struct net *net;
 
-	down_read(&net_rwsem);
-	for_each_net(net) {
-		struct wext_net *wnet = wext_net(net);
 
-		while ((skb = skb_dequeue(&wnet->nlevents)))
-			rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL,
-				    GFP_KERNEL);
-	}
-	up_read(&net_rwsem);
+	while ((skb = skb_dequeue(&wnet->nlevents)))
+		rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL, GFP_KERNEL);
 }
 EXPORT_SYMBOL_GPL(wireless_nlevent_flush);
 
 static int wext_netdev_notifier_call(struct notifier_block *nb,
 				     unsigned long state, void *ptr)
 {
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+
 	/*
 	 * When a netdev changes state in any way, flush all pending messages
 	 * to avoid them going out in a strange order, e.g. RTM_NEWLINK after
@@ -383,7 +380,7 @@ static int wext_netdev_notifier_call(struct notifier_block *nb,
 	 * or similar - all of which could otherwise happen due to delays from
 	 * schedule_work().
 	 */
-	wireless_nlevent_flush();
+	wireless_nlevent_flush(dev_net(dev));
 
 	return NOTIFY_OK;
 }
@@ -395,13 +392,17 @@ static struct notifier_block wext_netdev_notifier = {
 /* Process events generated by the wireless layer or the driver. */
 static void wireless_nlevent_process(struct work_struct *work)
 {
-	wireless_nlevent_flush();
+	struct wext_net *wnet;
+
+	wnet = container_of(work, struct wext_net, nlevent_work);
+	wireless_nlevent_flush(wnet->net);
 }
 
 static int __net_init wext_pernet_init(struct net *net)
 {
 	struct wext_net *wnet = wext_net(net);
 
+	wnet->net = net;
 	skb_queue_head_init(&wnet->nlevents);
 	INIT_WORK(&wnet->nlevent_work, wireless_nlevent_process);
 
-- 
2.39.5 (Apple Git-154)