netdev - [PATCH v3 net-next 20/23] net: linkwatch: add net device refcount tracker

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Message-Id: <20211205042217.982127-21-eric.dumazet@gmail.com>
Date:   Sat,  4 Dec 2021 20:22:14 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH v3 net-next 20/23] net: linkwatch: add net device refcount tracker

From: Eric Dumazet <edumazet@...gle.com>

Add a netdevice_tracker inside struct net_device, to track
the self reference when a device is in lweventlist.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/linux/netdevice.h | 2 ++
 net/core/link_watch.c     | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index afed3b10491b92da880a8cd13181ff041cc54673..cc17f26cd4ad59a4d1868951fee13f56ab73cd1a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1950,6 +1950,7 @@ enum netdev_ml_priv_type {
  *			keep a list of interfaces to be deleted.
  *
  *	@dev_addr_shadow:	Copy of @dev_addr to catch direct writes.
+ *	linkwatch_dev_tracker:	refcount tracker used by linkwatch.
  *
  *	FIXME: cleanup struct net_device such that network protocol info
  *	moves out.
@@ -2280,6 +2281,7 @@ struct net_device {
 	struct bpf_xdp_entity	xdp_state[__MAX_XDP_MODE];
 
 	u8 dev_addr_shadow[MAX_ADDR_LEN];
+	netdevice_tracker	linkwatch_dev_tracker;
 };
 #define to_net_dev(d) container_of(d, struct net_device, dev)
 
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 9599afd0862dabfca4560de6ec36606bf3742fd6..d7d089963b1da4142a0863715382aa81241625eb 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -109,7 +109,7 @@ static void linkwatch_add_event(struct net_device *dev)
 	spin_lock_irqsave(&lweventlist_lock, flags);
 	if (list_empty(&dev->link_watch_list)) {
 		list_add_tail(&dev->link_watch_list, &lweventlist);
-		dev_hold(dev);
+		dev_hold_track(dev, &dev->linkwatch_dev_tracker, GFP_ATOMIC);
 	}
 	spin_unlock_irqrestore(&lweventlist_lock, flags);
 }
@@ -166,7 +166,7 @@ static void linkwatch_do_dev(struct net_device *dev)
 
 		netdev_state_change(dev);
 	}
-	dev_put(dev);
+	dev_put_track(dev, &dev->linkwatch_dev_tracker);
 }
 
 static void __linkwatch_run_queue(int urgent_only)
-- 
2.34.1.400.ga245620fadb-goog