l2tp: fix locking of 64-bit counters for smp

L2TP uses 64-bit counters but since these are not updated atomically,
we need to make them safe for smp. This patch addresses that.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 103 insertions, 35 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 0ca9bc39150f..f1bfae3e1ba6 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -330,8 +330,10 @@ static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *sk
         struct sk_buff *skbp;
         struct sk_buff *tmp;
         u32 ns = L2TP_SKB_CB(skb)->ns;
+        struct l2tp_stats *sstats;
 
         spin_lock_bh(&session->reorder_q.lock);
+        sstats = &session->stats;
         skb_queue_walk_safe(&session->reorder_q, skbp, tmp) {
                 if (L2TP_SKB_CB(skbp)->ns > ns) {
                         __skb_queue_before(&session->reorder_q, skbp, skb);
@@ -339,7 +341,9 @@ static void l2tp_recv_queue_skb(struct l2tp_session *session, struct sk_buff *sk
                                "%s: pkt %hu, inserted before %hu, reorder_q len=%d\n",
                                session->name, ns, L2TP_SKB_CB(skbp)->ns,
                                skb_queue_len(&session->reorder_q));
-                        session->stats.rx_oos_packets++;
+                        u64_stats_update_begin(&sstats->syncp);
+                        sstats->rx_oos_packets++;
+                        u64_stats_update_end(&sstats->syncp);
                         goto out;
                 }
         }
@@ -356,16 +360,23 @@ static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *
 {
         struct l2tp_tunnel *tunnel = session->tunnel;
         int length = L2TP_SKB_CB(skb)->length;
+        struct l2tp_stats *tstats, *sstats;
 
         /* We're about to requeue the skb, so return resources
          * to its current owner (a socket receive buffer).
          */
         skb_orphan(skb);
 
-        tunnel->stats.rx_packets++;
-        tunnel->stats.rx_bytes += length;
-        session->stats.rx_packets++;
-        session->stats.rx_bytes += length;
+        tstats = &tunnel->stats;
+        u64_stats_update_begin(&tstats->syncp);
+        sstats = &session->stats;
+        u64_stats_update_begin(&sstats->syncp);
+        tstats->rx_packets++;
+        tstats->rx_bytes += length;
+        sstats->rx_packets++;
+        sstats->rx_bytes += length;
+        u64_stats_update_end(&tstats->syncp);
+        u64_stats_update_end(&sstats->syncp);
 
         if (L2TP_SKB_CB(skb)->has_seq) {
                 /* Bump our Nr */
@@ -396,6 +407,7 @@ static void l2tp_recv_dequeue(struct l2tp_session *session)
 {
         struct sk_buff *skb;
         struct sk_buff *tmp;
+        struct l2tp_stats *sstats;
 
         /* If the pkt at the head of the queue has the nr that we
          * expect to send up next, dequeue it and any other
@@ -403,10 +415,13 @@ static void l2tp_recv_dequeue(struct l2tp_session *session)
          */
 start:
         spin_lock_bh(&session->reorder_q.lock);
+        sstats = &session->stats;
         skb_queue_walk_safe(&session->reorder_q, skb, tmp) {
                 if (time_after(jiffies, L2TP_SKB_CB(skb)->expires)) {
-                        session->stats.rx_seq_discards++;
-                        session->stats.rx_errors++;
+                        u64_stats_update_begin(&sstats->syncp);
+                        sstats->rx_seq_discards++;
+                        sstats->rx_errors++;
+                        u64_stats_update_end(&sstats->syncp);
                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
                                "%s: oos pkt %u len %d discarded (too old), "
                                "waiting for %u, reorder_q_len=%d\n",
@@ -558,6 +573,7 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
         struct l2tp_tunnel *tunnel = session->tunnel;
         int offset;
         u32 ns, nr;
+        struct l2tp_stats *sstats = &session->stats;
 
         /* The ref count is increased since we now hold a pointer to
          * the session. Take care to decrement the refcnt when exiting
@@ -573,7 +589,9 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
                         PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
                                "%s: cookie mismatch (%u/%u). Discarding.\n",
                                tunnel->name, tunnel->tunnel_id, session->session_id);
-                        session->stats.rx_cookie_discards++;
+                        u64_stats_update_begin(&sstats->syncp);
+                        sstats->rx_cookie_discards++;
+                        u64_stats_update_end(&sstats->syncp);
                         goto discard;
                 }
                 ptr += session->peer_cookie_len;
@@ -642,7 +660,9 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
                                "%s: recv data has no seq numbers when required. "
                                "Discarding\n", session->name);
-                        session->stats.rx_seq_discards++;
+                        u64_stats_update_begin(&sstats->syncp);
+                        sstats->rx_seq_discards++;
+                        u64_stats_update_end(&sstats->syncp);
                         goto discard;
                 }
 
@@ -661,7 +681,9 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
                         PRINTK(session->debug, L2TP_MSG_SEQ, KERN_WARNING,
                                "%s: recv data has no seq numbers when required. "
                                "Discarding\n", session->name);
-                        session->stats.rx_seq_discards++;
+                        u64_stats_update_begin(&sstats->syncp);
+                        sstats->rx_seq_discards++;
+                        u64_stats_update_end(&sstats->syncp);
                         goto discard;
                 }
         }
@@ -715,7 +737,9 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
                          * packets
                          */
                         if (L2TP_SKB_CB(skb)->ns != session->nr) {
-                                session->stats.rx_seq_discards++;
+                                u64_stats_update_begin(&sstats->syncp);
+                                sstats->rx_seq_discards++;
+                                u64_stats_update_end(&sstats->syncp);
                                 PRINTK(session->debug, L2TP_MSG_SEQ, KERN_DEBUG,
                                        "%s: oos pkt %u len %d discarded, "
                                        "waiting for %u, reorder_q_len=%d\n",
@@ -742,7 +766,9 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
         return;
 
 discard:
-        session->stats.rx_errors++;
+        u64_stats_update_begin(&sstats->syncp);
+        sstats->rx_errors++;
+        u64_stats_update_end(&sstats->syncp);
         kfree_skb(skb);
 
         if (session->deref)
@@ -768,6 +794,7 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
         int offset;
         u16 version;
         int length;
+        struct l2tp_stats *tstats;
 
         if (tunnel->sock && l2tp_verify_udp_checksum(tunnel->sock, skb))
                 goto discard_bad_csum;
@@ -860,7 +887,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 discard_bad_csum:
         LIMIT_NETDEBUG("%s: UDP: bad checksum\n", tunnel->name);
         UDP_INC_STATS_USER(tunnel->l2tp_net, UDP_MIB_INERRORS, 0);
-        tunnel->stats.rx_errors++;
+        tstats = &tunnel->stats;
+        u64_stats_update_begin(&tstats->syncp);
+        tstats->rx_errors++;
+        u64_stats_update_end(&tstats->syncp);
         kfree_skb(skb);
 
         return 0;
@@ -986,6 +1016,7 @@ static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
         struct l2tp_tunnel *tunnel = session->tunnel;
         unsigned int len = skb->len;
         int error;
+        struct l2tp_stats *tstats, *sstats;
 
         /* Debug */
         if (session->send_seq)
@@ -1022,15 +1053,21 @@ static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
                 error = ip_queue_xmit(skb, fl);
 
         /* Update stats */
+        tstats = &tunnel->stats;
+        u64_stats_update_begin(&tstats->syncp);
+        sstats = &session->stats;
+        u64_stats_update_begin(&sstats->syncp);
         if (error >= 0) {
-                tunnel->stats.tx_packets++;
-                tunnel->stats.tx_bytes += len;
-                session->stats.tx_packets++;
-                session->stats.tx_bytes += len;
+                tstats->tx_packets++;
+                tstats->tx_bytes += len;
+                sstats->tx_packets++;
+                sstats->tx_bytes += len;
         } else {
-                tunnel->stats.tx_errors++;
-                session->stats.tx_errors++;
+                tstats->tx_errors++;
+                sstats->tx_errors++;
         }
+        u64_stats_update_end(&tstats->syncp);
+        u64_stats_update_end(&sstats->syncp);
 
         return 0;
 }
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 09e4a38b4f43..a8c943bf4140 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -45,6 +45,7 @@ struct l2tp_stats {
         u64                     rx_oos_packets;
         u64                     rx_errors;
         u64                     rx_cookie_discards;
+        struct u64_stats_sync   syncp;
 };
 
 struct l2tp_tunnel;
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index bc8c3348f835..1dbb9772fc45 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -225,6 +225,8 @@ static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 pid, u32 seq, int flags,
         struct nlattr *nest;
         struct sock *sk = NULL;
         struct inet_sock *inet;
+        struct l2tp_stats stats;
+        unsigned int start;
 
         hdr = genlmsg_put(skb, pid, seq, &l2tp_nl_family, flags,
                           L2TP_CMD_TUNNEL_GET);
@@ -242,16 +244,28 @@ static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 pid, u32 seq, int flags,
         if (nest == NULL)
                 goto nla_put_failure;
 
-        if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS, tunnel->stats.tx_packets) ||
-            nla_put_u64(skb, L2TP_ATTR_TX_BYTES, tunnel->stats.tx_bytes) ||
-            nla_put_u64(skb, L2TP_ATTR_TX_ERRORS, tunnel->stats.tx_errors) ||
-            nla_put_u64(skb, L2TP_ATTR_RX_PACKETS, tunnel->stats.rx_packets) ||
-            nla_put_u64(skb, L2TP_ATTR_RX_BYTES, tunnel->stats.rx_bytes) ||
+        do {
+                start = u64_stats_fetch_begin(&tunnel->stats.syncp);
+                stats.tx_packets = tunnel->stats.tx_packets;
+                stats.tx_bytes = tunnel->stats.tx_bytes;
+                stats.tx_errors = tunnel->stats.tx_errors;
+                stats.rx_packets = tunnel->stats.rx_packets;
+                stats.rx_bytes = tunnel->stats.rx_bytes;
+                stats.rx_errors = tunnel->stats.rx_errors;
+                stats.rx_seq_discards = tunnel->stats.rx_seq_discards;
+                stats.rx_oos_packets = tunnel->stats.rx_oos_packets;
+        } while (u64_stats_fetch_retry(&tunnel->stats.syncp, start));
+
+        if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS, stats.tx_packets) ||
+            nla_put_u64(skb, L2TP_ATTR_TX_BYTES, stats.tx_bytes) ||
+            nla_put_u64(skb, L2TP_ATTR_TX_ERRORS, stats.tx_errors) ||
+            nla_put_u64(skb, L2TP_ATTR_RX_PACKETS, stats.rx_packets) ||
+            nla_put_u64(skb, L2TP_ATTR_RX_BYTES, stats.rx_bytes) ||
             nla_put_u64(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
-                        tunnel->stats.rx_seq_discards) ||
+                        stats.rx_seq_discards) ||
             nla_put_u64(skb, L2TP_ATTR_RX_OOS_PACKETS,
-                        tunnel->stats.rx_oos_packets) ||
-            nla_put_u64(skb, L2TP_ATTR_RX_ERRORS, tunnel->stats.rx_errors))
+                        stats.rx_oos_packets) ||
+            nla_put_u64(skb, L2TP_ATTR_RX_ERRORS, stats.rx_errors))
                 goto nla_put_failure;
         nla_nest_end(skb, nest);
 
@@ -563,6 +577,8 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 pid, u32 seq, int flags
         struct nlattr *nest;
         struct l2tp_tunnel *tunnel = session->tunnel;
         struct sock *sk = NULL;
+        struct l2tp_stats stats;
+        unsigned int start;
 
         sk = tunnel->sock;
 
@@ -600,19 +616,33 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 pid, u32 seq, int flags
             (session->reorder_timeout &&
              nla_put_msecs(skb, L2TP_ATTR_RECV_TIMEOUT, session->reorder_timeout)))
                 goto nla_put_failure;
+
         nest = nla_nest_start(skb, L2TP_ATTR_STATS);
         if (nest == NULL)
                 goto nla_put_failure;
-        if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS, session->stats.tx_packets) ||
-            nla_put_u64(skb, L2TP_ATTR_TX_BYTES, session->stats.tx_bytes) ||
-            nla_put_u64(skb, L2TP_ATTR_TX_ERRORS, session->stats.tx_errors) ||
-            nla_put_u64(skb, L2TP_ATTR_RX_PACKETS, session->stats.rx_packets) ||
-            nla_put_u64(skb, L2TP_ATTR_RX_BYTES, session->stats.rx_bytes) ||
+
+        do {
+                start = u64_stats_fetch_begin(&session->stats.syncp);
+                stats.tx_packets = session->stats.tx_packets;
+                stats.tx_bytes = session->stats.tx_bytes;
+                stats.tx_errors = session->stats.tx_errors;
+                stats.rx_packets = session->stats.rx_packets;
+                stats.rx_bytes = session->stats.rx_bytes;
+                stats.rx_errors = session->stats.rx_errors;
+                stats.rx_seq_discards = session->stats.rx_seq_discards;
+                stats.rx_oos_packets = session->stats.rx_oos_packets;
+        } while (u64_stats_fetch_retry(&session->stats.syncp, start));
+
+        if (nla_put_u64(skb, L2TP_ATTR_TX_PACKETS, stats.tx_packets) ||
+            nla_put_u64(skb, L2TP_ATTR_TX_BYTES, stats.tx_bytes) ||
+            nla_put_u64(skb, L2TP_ATTR_TX_ERRORS, stats.tx_errors) ||
+            nla_put_u64(skb, L2TP_ATTR_RX_PACKETS, stats.rx_packets) ||
+            nla_put_u64(skb, L2TP_ATTR_RX_BYTES, stats.rx_bytes) ||
             nla_put_u64(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
-                        session->stats.rx_seq_discards) ||
+                        stats.rx_seq_discards) ||
             nla_put_u64(skb, L2TP_ATTR_RX_OOS_PACKETS,
-                        session->stats.rx_oos_packets) ||
-            nla_put_u64(skb, L2TP_ATTR_RX_ERRORS, session->stats.rx_errors))
+                        stats.rx_oos_packets) ||
+            nla_put_u64(skb, L2TP_ATTR_RX_ERRORS, stats.rx_errors))
                 goto nla_put_failure;
         nla_nest_end(skb, nest);