netdev - [PATCH net-next 3/3] net: netpoll: flush skb pool during cleanup

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Message-ID: <20241025142025.3558051-4-leitao@debian.org>
Date: Fri, 25 Oct 2024 07:20:20 -0700
From: Breno Leitao <leitao@...ian.org>
To: kuba@...nel.org,
	horms@...nel.org,
	davem@...emloft.net,
	edumazet@...gle.com,
	pabeni@...hat.com
Cc: thepacketgeek@...il.com,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	davej@...emonkey.org.uk,
	vlad.wing@...il.com,
	max@...sevol.com,
	kernel-team@...a.com,
	jiri@...nulli.us,
	jv@...sburgh.net,
	andy@...yhouse.net,
	aehkn@...hub.one,
	Rik van Riel <riel@...riel.com>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH net-next 3/3] net: netpoll: flush skb pool during cleanup

The netpoll subsystem maintains a pool of 32 pre-allocated SKBs per
instance, but these SKBs are not freed when the netpoll user is brought
down. This leads to memory waste as these buffers remain allocated but
unused.

Add skb_pool_flush() to properly clean up these SKBs when netconsole is
terminated, improving memory efficiency.

Signed-off-by: Breno Leitao <leitao@...ian.org>
---
 net/core/netpoll.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index c9a9e37e2d74..bf2064d689d5 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -656,6 +656,7 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
 
 	/* last thing to do is link it to the net device structure */
 	rcu_assign_pointer(ndev->npinfo, npinfo);
+	skb_queue_head_init(&np->skb_pool);
 
 	return 0;
 
@@ -809,6 +810,22 @@ static void rcu_cleanup_netpoll_info(struct rcu_head *rcu_head)
 	kfree(npinfo);
 }
 
+static void skb_pool_flush(struct netpoll *np)
+{
+	struct sk_buff_head *skb_pool;
+	struct sk_buff *skb;
+	unsigned long flags;
+
+	skb_pool = &np->skb_pool;
+
+	spin_lock_irqsave(&skb_pool->lock, flags);
+	while (skb_pool->qlen > 0) {
+		skb = __skb_dequeue(skb_pool);
+		kfree_skb(skb);
+	}
+	spin_unlock_irqrestore(&skb_pool->lock, flags);
+}
+
 void __netpoll_cleanup(struct netpoll *np)
 {
 	struct netpoll_info *npinfo;
@@ -828,6 +845,8 @@ void __netpoll_cleanup(struct netpoll *np)
 		call_rcu(&npinfo->rcu, rcu_cleanup_netpoll_info);
 	} else
 		RCU_INIT_POINTER(np->dev->npinfo, NULL);
+
+	skb_pool_flush(np);
 }
 EXPORT_SYMBOL_GPL(__netpoll_cleanup);
 
-- 
2.43.5