linux-kernel - [PATCH 6/7] netpoll: Move find_skb() to netconsole and make it static

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Message-Id: <20250902-netpoll_untangle_v3-v1-6-51a03d6411be@debian.org>
Date: Tue, 02 Sep 2025 07:36:28 -0700
From: Breno Leitao <leitao@...ian.org>
To: 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>, 
 Simon Horman <horms@...nel.org>, 
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
 Clark Williams <clrkwllms@...nel.org>, Steven Rostedt <rostedt@...dmis.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-rt-devel@...ts.linux.dev, kernel-team@...a.com, efault@....de, 
 calvin@...nvd.org, Breno Leitao <leitao@...ian.org>
Subject: [PATCH 6/7] netpoll: Move find_skb() to netconsole and make it
 static

Complete the SKB pool management refactoring by moving find_skb() from
netpoll core to netconsole driver, making it a static function.

This is the final step in removing SKB pool management from the generic
netpoll infrastructure. With this change:

1. Netpoll core is now purely transmission-focused: Contains only
   the essential netpoll_send_skb() function for low-level packet
   transmission, with no knowledge of SKB allocation or pool management.

2. Complete encapsulation in netconsole: All SKB lifecycle
   management (allocation, pool handling, packet construction) is now
   contained within the netconsole driver where it belongs.

3. Cleaner API surface: Removes the last SKB management export from
   netpoll, leaving only zap_completion_queue() as a utility function
   and netpoll_send_skb() for transmission.

4. Better maintainability: Changes to SKB allocation strategies or
   pool management can now be made entirely within netconsole without
   affecting the core netpoll infrastructure.

The find_skb() function is made static since it's now only used within
netconsole.c for its internal SKB allocation needs.

This completes the architectural cleanup that separates generic netpoll
transmission capabilities from console-specific resource management.

Signed-off-by: Breno Leitao <leitao@...ian.org>
---
 drivers/net/netconsole.c | 27 +++++++++++++++++++++++++++
 include/linux/netpoll.h  |  1 -
 net/core/netpoll.c       | 28 ----------------------------
 3 files changed, 27 insertions(+), 29 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 3fe55db07cfe5..bf7bab7a9c2f0 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1655,6 +1655,33 @@ static void push_eth(struct netpoll *np, struct sk_buff *skb)
 		eth->h_proto = htons(ETH_P_IP);
 }

+static struct sk_buff *find_skb(struct netpoll *np, int len, int reserve)
+{
+	int count = 0;
+	struct sk_buff *skb;
+
+	zap_completion_queue();
+repeat:
+
+	skb = alloc_skb(len, GFP_ATOMIC);
+	if (!skb) {
+		skb = skb_dequeue(&np->skb_pool);
+		schedule_work(&np->refill_wq);
+	}
+
+	if (!skb) {
+		if (++count < 10) {
+			netpoll_poll_dev(np->dev);
+			goto repeat;
+		}
+		return NULL;
+	}
+
+	refcount_set(&skb->users, 1);
+	skb_reserve(skb, reserve);
+	return skb;
+}
+
 static struct sk_buff *netpoll_prepare_skb(struct netpoll *np, const char *msg,
 					   int len)
 {
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 7f8b4d758a1e7..f89bc9fb1f773 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -74,7 +74,6 @@ int netpoll_setup(struct netpoll *np);
 void __netpoll_free(struct netpoll *np);
 void do_netpoll_cleanup(struct netpoll *np);
 netdev_tx_t netpoll_send_skb(struct netpoll *np, struct sk_buff *skb);
-struct sk_buff *find_skb(struct netpoll *np, int len, int reserve);
 void zap_completion_queue(void);

 #ifdef CONFIG_NETPOLL
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 94c75f39787bb..5aa83c9c09e05 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -235,34 +235,6 @@ void zap_completion_queue(void)
 }
 EXPORT_SYMBOL_GPL(zap_completion_queue);

-struct sk_buff *find_skb(struct netpoll *np, int len, int reserve)
-{
-	int count = 0;
-	struct sk_buff *skb;
-
-	zap_completion_queue();
-repeat:
-
-	skb = alloc_skb(len, GFP_ATOMIC);
-	if (!skb) {
-		skb = skb_dequeue(&np->skb_pool);
-		schedule_work(&np->refill_wq);
-	}
-
-	if (!skb) {
-		if (++count < 10) {
-			netpoll_poll_dev(np->dev);
-			goto repeat;
-		}
-		return NULL;
-	}
-
-	refcount_set(&skb->users, 1);
-	skb_reserve(skb, reserve);
-	return skb;
-}
-EXPORT_SYMBOL_GPL(find_skb);
-
 static int netpoll_owner_active(struct net_device *dev)
 {
 	struct napi_struct *napi;

-- 
2.47.3