nfp: flower: split and limit cmsg skb lists

Introduce a second skb list for handling control messages and limit the
number of allowed messages. Some control messages are considered more
crucial than others, resulting in the need for a second skb list. By
splitting the list into a separate high and low priority list we can
ensure that messages on the high list get added to the head of the list
that gets processed, this however has no functional impact. Previously
there was no limit on the number of messages allowed on the queue, this
could result in the queue growing boundlessly and eventually the host
running out of memory.

Fixes: b985f870a5f0 ("nfp: process control messages in workqueue in flower app")
Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/flower/cmsg.c

@@ -272,18 +272,49 @@ out:
 
 void nfp_flower_cmsg_process_rx(struct work_struct *work)
 {
+	struct sk_buff_head cmsg_joined;
 	struct nfp_flower_priv *priv;
 	struct sk_buff *skb;
 
 	priv = container_of(work, struct nfp_flower_priv, cmsg_work);
+	skb_queue_head_init(&cmsg_joined);
 
-	while ((skb = skb_dequeue(&priv->cmsg_skbs)))
+	spin_lock_bh(&priv->cmsg_skbs_high.lock);
+	skb_queue_splice_tail_init(&priv->cmsg_skbs_high, &cmsg_joined);
+	spin_unlock_bh(&priv->cmsg_skbs_high.lock);
+
+	spin_lock_bh(&priv->cmsg_skbs_low.lock);
+	skb_queue_splice_tail_init(&priv->cmsg_skbs_low, &cmsg_joined);
+	spin_unlock_bh(&priv->cmsg_skbs_low.lock);
+
+	while ((skb = __skb_dequeue(&cmsg_joined)))
 		nfp_flower_cmsg_process_one_rx(priv->app, skb);
 }
 
-void nfp_flower_cmsg_rx(struct nfp_app *app, struct sk_buff *skb)
+static void
+nfp_flower_queue_ctl_msg(struct nfp_app *app, struct sk_buff *skb, int type)
 {
 	struct nfp_flower_priv *priv = app->priv;
+	struct sk_buff_head *skb_head;
+
+	if (type == NFP_FLOWER_CMSG_TYPE_PORT_REIFY ||
+	    type == NFP_FLOWER_CMSG_TYPE_PORT_MOD)
+		skb_head = &priv->cmsg_skbs_high;
+	else
+		skb_head = &priv->cmsg_skbs_low;
+
+	if (skb_queue_len(skb_head) >= NFP_FLOWER_WORKQ_MAX_SKBS) {
+		nfp_flower_cmsg_warn(app, "Dropping queued control messages\n");
+		dev_kfree_skb_any(skb);
+		return;
+	}
+
+	skb_queue_tail(skb_head, skb);
+	schedule_work(&priv->cmsg_work);
+}
+
+void nfp_flower_cmsg_rx(struct nfp_app *app, struct sk_buff *skb)
+{
 	struct nfp_flower_cmsg_hdr *cmsg_hdr;
 
 	cmsg_hdr = nfp_flower_cmsg_get_hdr(skb);
@@ -307,7 +338,6 @@ void nfp_flower_cmsg_rx(struct nfp_app *app, struct sk_buff *skb)
 		/* Acks from the NFP that the route is added - ignore. */
 		dev_consume_skb_any(skb);
 	} else {
-		skb_queue_tail(&priv->cmsg_skbs, skb);
-		schedule_work(&priv->cmsg_work);
+		nfp_flower_queue_ctl_msg(app, skb, cmsg_hdr->type);
 	}
 }

drivers/net/ethernet/netronome/nfp/flower/cmsg.h

@@ -108,6 +108,8 @@
 #define NFP_FL_IPV4_TUNNEL_TYPE		GENMASK(7, 4)
 #define NFP_FL_IPV4_PRE_TUN_INDEX	GENMASK(2, 0)
 
+#define NFP_FLOWER_WORKQ_MAX_SKBS	30000
+
 #define nfp_flower_cmsg_warn(app, fmt, args...)                         \
 	do {                                                            \
 		if (net_ratelimit())                                    \

drivers/net/ethernet/netronome/nfp/flower/main.c

@@ -519,7 +519,8 @@ static int nfp_flower_init(struct nfp_app *app)
 
 	app->priv = app_priv;
 	app_priv->app = app;
-	skb_queue_head_init(&app_priv->cmsg_skbs);
+	skb_queue_head_init(&app_priv->cmsg_skbs_high);
+	skb_queue_head_init(&app_priv->cmsg_skbs_low);
 	INIT_WORK(&app_priv->cmsg_work, nfp_flower_cmsg_process_rx);
 	init_waitqueue_head(&app_priv->reify_wait_queue);
 
@@ -549,7 +550,8 @@ static void nfp_flower_clean(struct nfp_app *app)
 {
 	struct nfp_flower_priv *app_priv = app->priv;
 
-	skb_queue_purge(&app_priv->cmsg_skbs);
+	skb_queue_purge(&app_priv->cmsg_skbs_high);
+	skb_queue_purge(&app_priv->cmsg_skbs_low);
 	flush_work(&app_priv->cmsg_work);
 
 	nfp_flower_metadata_cleanup(app);

drivers/net/ethernet/netronome/nfp/flower/main.h

@@ -107,7 +107,10 @@ struct nfp_mtu_conf {
  * @mask_table:		Hash table used to store masks
  * @flow_table:		Hash table used to store flower rules
  * @cmsg_work:		Workqueue for control messages processing
- * @cmsg_skbs:		List of skbs for control message processing
+ * @cmsg_skbs_high:	List of higher priority skbs for control message
+ *			processing
+ * @cmsg_skbs_low:	List of lower priority skbs for control message
+ *			processing
  * @nfp_mac_off_list:	List of MAC addresses to offload
  * @nfp_mac_index_list:	List of unique 8-bit indexes for non NFP netdevs
  * @nfp_ipv4_off_list:	List of IPv4 addresses to offload
@@ -136,7 +139,8 @@ struct nfp_flower_priv {
 	DECLARE_HASHTABLE(mask_table, NFP_FLOWER_MASK_HASH_BITS);
 	DECLARE_HASHTABLE(flow_table, NFP_FLOWER_HASH_BITS);
 	struct work_struct cmsg_work;
-	struct sk_buff_head cmsg_skbs;
+	struct sk_buff_head cmsg_skbs_high;
+	struct sk_buff_head cmsg_skbs_low;
 	struct list_head nfp_mac_off_list;
 	struct list_head nfp_mac_index_list;
 	struct list_head nfp_ipv4_off_list;