[PATCH net-next v2 4/8] netconsole: move refill_skbs() and skb-pool sizing macros from netpoll

[Breno Leitao <leitao@debian.org>]

refill_skbs() is now only called from netconsole (directly via
netconsole_skb_pool_init() and indirectly via the just-moved
refill_skbs_work_handler()), and the MAX_UDP_CHUNK / MAX_SKBS /
MAX_SKB_SIZE macros are private to it. Move them all into
drivers/net/netconsole.c.

MAX_UDP_CHUNK and MAX_SKB_SIZE were promoted to <linux/netpoll.h>
by commit 6c537b845c99 ("netconsole: do not dequeue pooled skbs that
cannot satisfy len") so find_skb() could detect oversized requests
against the same value refill_skbs() used. With both functions now
local to netconsole, the shared definition no longer needs to live
in the header.

Pure code motion: bodies and pool sizing semantics are unchanged.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 drivers/net/netconsole.c | 29 +++++++++++++++++++++++++++++
 include/linux/netpoll.h  | 15 ---------------
 net/core/netpoll.c       | 23 -----------------------
 3 files changed, 29 insertions(+), 38 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 59b1f7d6f103a..6bb8184d023a3 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -61,6 +61,19 @@ MODULE_IMPORT_NS("NETDEV_INTERNAL");
 #define MAX_USERDATA_ITEMS		256
 #define MAX_PRINT_CHUNK			1000
 
+/*
+ * Sizing for the per-target fallback skb pool consulted by find_skb()
+ * when its GFP_ATOMIC allocation fails so messages still get out under
+ * memory pressure.
+ */
+#define MAX_UDP_CHUNK			1460
+#define MAX_SKBS			32
+#define MAX_SKB_SIZE							\
+	(sizeof(struct ethhdr) +					\
+	 sizeof(struct iphdr) +						\
+	 sizeof(struct udphdr) +					\
+	 MAX_UDP_CHUNK)
+
 static char config[MAX_PARAM_LENGTH];
 module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0);
 MODULE_PARM_DESC(netconsole, " netconsole=[src-port]@[src-ip]/[dev],[tgt-port]@<tgt-ip>/[tgt-macaddr]");
@@ -292,6 +305,22 @@ static void netcons_release_dev(struct netconsole_target *nt)
 		memset(&nt->np.dev_name, 0, IFNAMSIZ);
 }
 
+static void refill_skbs(struct netpoll *np)
+{
+	struct sk_buff_head *skb_pool;
+	struct sk_buff *skb;
+
+	skb_pool = &np->skb_pool;
+
+	while (READ_ONCE(skb_pool->qlen) < MAX_SKBS) {
+		skb = alloc_skb(MAX_SKB_SIZE, GFP_ATOMIC | __GFP_NOWARN);
+		if (!skb)
+			break;
+
+		skb_queue_tail(skb_pool, skb);
+	}
+}
+
 static void refill_skbs_work_handler(struct work_struct *work)
 {
 	struct netpoll *np =
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 51e5863d8e678..7e2fbce863e9b 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -21,20 +21,6 @@ union inet_addr {
 	struct in6_addr	in6;
 };
 
-/*
- * Maximum payload netpoll's preallocated skb pool can carry. Keep this in
- * sync with the buffer size used by refill_skbs() in net/core/netpoll.c;
- * callers (e.g. netconsole) use it to detect requests the pool can never
- * satisfy and avoid dequeuing a pooled skb that would later trip
- * skb_over_panic() in skb_put().
- */
-#define MAX_UDP_CHUNK	1460
-#define MAX_SKB_SIZE						\
-	(sizeof(struct ethhdr) +				\
-	 sizeof(struct iphdr) +					\
-	 sizeof(struct udphdr) +				\
-	 MAX_UDP_CHUNK)
-
 struct netpoll {
 	struct net_device *dev;
 	netdevice_tracker dev_tracker;
@@ -90,7 +76,6 @@ void netpoll_cleanup(struct netpoll *np);
 void do_netpoll_cleanup(struct netpoll *np);
 netdev_tx_t netpoll_send_skb(struct netpoll *np, struct sk_buff *skb);
 void netpoll_zap_completion_queue(void);
-void refill_skbs(struct netpoll *np);
 void skb_pool_flush(struct netpoll *np);
 
 #ifdef CONFIG_NETPOLL
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 7088cf0df43ce..921699e69ac97 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -36,12 +36,6 @@
 #include <trace/events/napi.h>
 #include <linux/kconfig.h>
 
-/*
- * We maintain a small pool of fully-sized skbs, to make sure the
- * message gets out even in extreme OOM situations.
- */
-
-#define MAX_SKBS 32
 #define USEC_PER_POLL	50
 
 static unsigned int carrier_timeout = 4;
@@ -213,23 +207,6 @@ void netpoll_poll_enable(struct net_device *dev)
 		up(&ni->dev_lock);
 }
 
-void refill_skbs(struct netpoll *np)
-{
-	struct sk_buff_head *skb_pool;
-	struct sk_buff *skb;
-
-	skb_pool = &np->skb_pool;
-
-	while (READ_ONCE(skb_pool->qlen) < MAX_SKBS) {
-		skb = alloc_skb(MAX_SKB_SIZE, GFP_ATOMIC | __GFP_NOWARN);
-		if (!skb)
-			break;
-
-		skb_queue_tail(skb_pool, skb);
-	}
-}
-EXPORT_SYMBOL_GPL(refill_skbs);
-
 void netpoll_zap_completion_queue(void)
 {
 	unsigned long flags;

-- 
2.53.0-Meta