[PATCH ovpn net] ovpn: disable BHs when updating device drop stats

ovpn updates dev->dstats from both process and softirq contexts. In
particular, TCP paths may run from socket callbacks, workqueues or
strparser work, while UDP receive and ovpn's ndo_start_xmit path may
update the same per-device dstats from BH context.

Add ovpn device drop-stat helpers that disable BHs around
dev_dstats_rx_dropped() and dev_dstats_tx_dropped(), and use them for
drop accounting.

The successful RX dev_dstats_rx_add() update is already covered by the
BH-disabled section around gro_cells_receive(). For the successful TCP
TX dev_dstats_tx_add() update, replace the existing preempt-disabled
section with a BH-disabled one.

Signed-off-by: Ralf Lici <[email protected]>
---
 drivers/net/ovpn/io.c    | 12 ++++++------
 drivers/net/ovpn/stats.h | 16 ++++++++++++++++
 drivers/net/ovpn/tcp.c   | 10 +++++-----
 drivers/net/ovpn/udp.c   |  2 +-
 4 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c
index 22c555dd962e..a6b777a9c2d9 100644
--- a/drivers/net/ovpn/io.c
+++ b/drivers/net/ovpn/io.c
@@ -201,7 +201,7 @@ void ovpn_decrypt_post(void *data, int ret)
 	skb = NULL;
 drop:
 	if (unlikely(skb))
-		dev_dstats_rx_dropped(peer->ovpn->dev);
+		ovpn_dev_dstats_rx_dropped(peer->ovpn->dev);
 	kfree_skb(skb);
 drop_nocount:
 	if (likely(peer))
@@ -225,7 +225,7 @@ void ovpn_recv(struct ovpn_peer *peer, struct sk_buff *skb)
 		net_info_ratelimited("%s: no available key for peer %u, key-id: %u\n",
 				     netdev_name(peer->ovpn->dev), peer->id,
 				     key_id);
-		dev_dstats_rx_dropped(peer->ovpn->dev);
+		ovpn_dev_dstats_rx_dropped(peer->ovpn->dev);
 		kfree_skb(skb);
 		ovpn_peer_put(peer);
 		return;
@@ -301,7 +301,7 @@ void ovpn_encrypt_post(void *data, int ret)
 	rcu_read_unlock();
 err:
 	if (unlikely(skb))
-		dev_dstats_tx_dropped(peer->ovpn->dev);
+		ovpn_dev_dstats_tx_dropped(peer->ovpn->dev);
 	if (likely(peer))
 		ovpn_peer_put(peer);
 	if (likely(ks))
@@ -343,7 +343,7 @@ static void ovpn_send(struct ovpn_priv *ovpn, struct sk_buff *skb,
 	 */
 	skb_list_walk_safe(skb, curr, next) {
 		if (unlikely(!ovpn_encrypt_one(peer, curr))) {
-			dev_dstats_tx_dropped(ovpn->dev);
+			ovpn_dev_dstats_tx_dropped(ovpn->dev);
 			kfree_skb(curr);
 		}
 	}
@@ -414,7 +414,7 @@ netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev)
 		if (unlikely(!curr)) {
 			net_err_ratelimited("%s: skb_share_check failed for payload packet\n",
 					    netdev_name(dev));
-			dev_dstats_tx_dropped(ovpn->dev);
+			ovpn_dev_dstats_tx_dropped(ovpn->dev);
 			continue;
 		}
 
@@ -440,7 +440,7 @@ netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev)
 drop:
 	ovpn_peer_put(peer);
 drop_no_peer:
-	dev_dstats_tx_dropped(ovpn->dev);
+	ovpn_dev_dstats_tx_dropped(ovpn->dev);
 	skb_tx_error(skb);
 	kfree_skb_list(skb);
 	return NETDEV_TX_OK;
diff --git a/drivers/net/ovpn/stats.h b/drivers/net/ovpn/stats.h
index 53433d8b6c33..3a45b97c0056 100644
--- a/drivers/net/ovpn/stats.h
+++ b/drivers/net/ovpn/stats.h
@@ -11,6 +11,8 @@
 #ifndef _NET_OVPN_OVPNSTATS_H_
 #define _NET_OVPN_OVPNSTATS_H_
 
+#include <linux/netdevice.h>
+
 /* one stat */
 struct ovpn_peer_stat {
 	atomic64_t bytes;
@@ -44,4 +46,18 @@ static inline void ovpn_peer_stats_increment_tx(struct ovpn_peer_stats *stats,
 	ovpn_peer_stats_increment(&stats->tx, n);
 }
 
+static inline void ovpn_dev_dstats_tx_dropped(struct net_device *dev)
+{
+	local_bh_disable();
+	dev_dstats_tx_dropped(dev);
+	local_bh_enable();
+}
+
+static inline void ovpn_dev_dstats_rx_dropped(struct net_device *dev)
+{
+	local_bh_disable();
+	dev_dstats_rx_dropped(dev);
+	local_bh_enable();
+}
+
 #endif /* _NET_OVPN_OVPNSTATS_H_ */
diff --git a/drivers/net/ovpn/tcp.c b/drivers/net/ovpn/tcp.c
index 65054cc84be5..ec3fd845d468 100644
--- a/drivers/net/ovpn/tcp.c
+++ b/drivers/net/ovpn/tcp.c
@@ -152,7 +152,7 @@ static void ovpn_tcp_rcv(struct strparser *strp, struct sk_buff *skb)
 	if (WARN_ON(!ovpn_peer_hold(peer)))
 		goto err_nopeer;
 	schedule_work(&peer->tcp.defer_del_work);
-	dev_dstats_rx_dropped(peer->ovpn->dev);
+	ovpn_dev_dstats_rx_dropped(peer->ovpn->dev);
 err_nopeer:
 	kfree_skb(skb);
 }
@@ -298,9 +298,9 @@ static void ovpn_tcp_send_sock(struct ovpn_peer *peer, struct sock *sk)
 	} while (peer->tcp.out_msg.len > 0);
 
 	if (!peer->tcp.out_msg.len) {
-		preempt_disable();
+		local_bh_disable();
 		dev_dstats_tx_add(peer->ovpn->dev, skb->len);
-		preempt_enable();
+		local_bh_enable();
 	}
 
 	kfree_skb(peer->tcp.out_msg.skb);
@@ -331,7 +331,7 @@ static void ovpn_tcp_send_sock_skb(struct ovpn_peer *peer, struct sock *sk,
 		ovpn_tcp_send_sock(peer, sk);
 
 	if (peer->tcp.out_msg.skb) {
-		dev_dstats_tx_dropped(peer->ovpn->dev);
+		ovpn_dev_dstats_tx_dropped(peer->ovpn->dev);
 		kfree_skb(skb);
 		return;
 	}
@@ -353,7 +353,7 @@ void ovpn_tcp_send_skb(struct ovpn_peer *peer, struct sock *sk,
 	if (sock_owned_by_user(sk)) {
 		if (skb_queue_len(&peer->tcp.out_queue) >=
 		    READ_ONCE(net_hotdata.max_backlog)) {
-			dev_dstats_tx_dropped(peer->ovpn->dev);
+			ovpn_dev_dstats_tx_dropped(peer->ovpn->dev);
 			kfree_skb(skb);
 			goto unlock;
 		}
diff --git a/drivers/net/ovpn/udp.c b/drivers/net/ovpn/udp.c
index 493a5a0744af..7f69e8890b5b 100644
--- a/drivers/net/ovpn/udp.c
+++ b/drivers/net/ovpn/udp.c
@@ -125,7 +125,7 @@ static int ovpn_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	return 0;
 
 drop:
-	dev_dstats_rx_dropped(ovpn->dev);
+	ovpn_dev_dstats_rx_dropped(ovpn->dev);
 drop_noovpn:
 	kfree_skb(skb);
 	return 0;
-- 
2.54.0