linux-kernel - [PATCH net-next v2 4/6] netpoll: add wrapper around __netpoll

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Message-Id: <20250921-netcons-retrigger-v2-4-a0e84006237f@gmail.com>
Date: Sun, 21 Sep 2025 22:55:44 +0100
From: Andre Carvalho <asantostc@...il.com>
To: Breno Leitao <leitao@...ian.org>, Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Shuah Khan <shuah@...nel.org>, Simon Horman <horms@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Andre Carvalho <asantostc@...il.com>
Subject: [PATCH net-next v2 4/6] netpoll: add wrapper around
 __netpoll_setup with dev reference

Introduce __netpoll_setup_hold() which wraps __netpoll_setup() and
on success holds a reference to the device. This helper requires caller
to already hold RNTL and should be paired with netpoll_cleanup to ensure
proper handling of the reference.

This helper is going to be used by netconsole to setup netpoll in
response to a NETDEV_UP event. Since netconsole always perform cleanup
using netpoll_cleanup, this will ensure that reference counting is
correct and handled entirely inside netpoll.

Signed-off-by: Andre Carvalho <asantostc@...il.com>
---
 include/linux/netpoll.h |  1 +
 net/core/netpoll.c      | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index f22eec4660405eaa654eb7746cbfdc89113fe312..345e741126748c0ee8d55dba594d782bced4eeed 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -69,6 +69,7 @@ static inline void netpoll_poll_enable(struct net_device *dev) { return; }

 int netpoll_send_udp(struct netpoll *np, const char *msg, int len);
 int __netpoll_setup(struct netpoll *np, struct net_device *ndev);
+int __netpoll_setup_hold(struct netpoll *np, struct net_device *ndev);
 int netpoll_setup(struct netpoll *np);
 void __netpoll_free(struct netpoll *np);
 void netpoll_cleanup(struct netpoll *np);
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 60a05d3b7c2491096f79ea6cf82eeef222c3eac2..bf563c4259f6cb19c31613ff277eb5a0e2165e43 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -608,6 +608,26 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
 }
 EXPORT_SYMBOL_GPL(__netpoll_setup);

+/*
+ * Wrapper around __netpoll_setup that holds a reference to the device.
+ * The caller must pair this with netpoll_cleanup() to release the reference.
+ */
+int __netpoll_setup_hold(struct netpoll *np, struct net_device *ndev)
+{
+	int err;
+
+	ASSERT_RTNL();
+
+	err = __netpoll_setup(np, ndev);
+	if (err)
+		return err;
+
+	netdev_hold(ndev, &np->dev_tracker, GFP_KERNEL);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__netpoll_setup_hold);
+
 /*
  * Returns a pointer to a string representation of the identifier used
  * to select the egress interface for the given netpoll instance. buf

-- 
2.51.0