[PATCH net-next v4 01/10] net: team: Annotate reads and writes for mixed lock accessed values

[Marc Harvey <marcharvey@google.com>]

The team_port's "index" and the team's "en_port_count" are read in
the hot transmit path, but are only written to when holding the rtnl
lock.

Use READ_ONCE() for all lockless reads of these values, and use
WRITE_ONCE() for all writes.

Signed-off-by: Marc Harvey <marcharvey@google.com>
---
Changes in v4:
- None

Changes in v3:
- None

Changes in v2:
- None
---
 drivers/net/team/team_core.c        | 11 ++++++-----
 drivers/net/team/team_mode_random.c |  2 +-
 include/linux/if_team.h             |  4 ++--
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/net/team/team_core.c b/drivers/net/team/team_core.c
index 566a5d102c23..becd066279a6 100644
--- a/drivers/net/team/team_core.c
+++ b/drivers/net/team/team_core.c
@@ -938,7 +938,8 @@ static void team_port_enable(struct team *team,
 {
 	if (team_port_enabled(port))
 		return;
-	port->index = team->en_port_count++;
+	WRITE_ONCE(port->index, team->en_port_count);
+	WRITE_ONCE(team->en_port_count, team->en_port_count + 1);
 	hlist_add_head_rcu(&port->hlist,
 			   team_port_index_hash(team, port->index));
 	team_adjust_ops(team);
@@ -958,7 +959,7 @@ static void __reconstruct_port_hlist(struct team *team, int rm_index)
 	for (i = rm_index + 1; i < team->en_port_count; i++) {
 		port = team_get_port_by_index(team, i);
 		hlist_del_rcu(&port->hlist);
-		port->index--;
+		WRITE_ONCE(port->index, port->index - 1);
 		hlist_add_head_rcu(&port->hlist,
 				   team_port_index_hash(team, port->index));
 	}
@@ -973,8 +974,8 @@ static void team_port_disable(struct team *team,
 		team->ops.port_disabled(team, port);
 	hlist_del_rcu(&port->hlist);
 	__reconstruct_port_hlist(team, port->index);
-	port->index = -1;
-	team->en_port_count--;
+	WRITE_ONCE(port->index, -1);
+	WRITE_ONCE(team->en_port_count, team->en_port_count - 1);
 	team_queue_override_port_del(team, port);
 	team_adjust_ops(team);
 	team_lower_state_changed(port);
@@ -1245,7 +1246,7 @@ static int team_port_add(struct team *team, struct net_device *port_dev,
 		netif_addr_unlock_bh(dev);
 	}
 
-	port->index = -1;
+	WRITE_ONCE(port->index, -1);
 	list_add_tail_rcu(&port->list, &team->port_list);
 	team_port_enable(team, port);
 	netdev_compute_master_upper_features(dev, true);
diff --git a/drivers/net/team/team_mode_random.c b/drivers/net/team/team_mode_random.c
index 53d0ce34b8ce..169a7bc865b2 100644
--- a/drivers/net/team/team_mode_random.c
+++ b/drivers/net/team/team_mode_random.c
@@ -16,7 +16,7 @@ static bool rnd_transmit(struct team *team, struct sk_buff *skb)
 	struct team_port *port;
 	int port_index;
 
-	port_index = get_random_u32_below(team->en_port_count);
+	port_index = get_random_u32_below(READ_ONCE(team->en_port_count));
 	port = team_get_port_by_index_rcu(team, port_index);
 	if (unlikely(!port))
 		goto drop;
diff --git a/include/linux/if_team.h b/include/linux/if_team.h
index ccb5327de26d..06f4d7400c1e 100644
--- a/include/linux/if_team.h
+++ b/include/linux/if_team.h
@@ -77,7 +77,7 @@ static inline struct team_port *team_port_get_rcu(const struct net_device *dev)
 
 static inline bool team_port_enabled(struct team_port *port)
 {
-	return port->index != -1;
+	return READ_ONCE(port->index) != -1;
 }
 
 static inline bool team_port_txable(struct team_port *port)
@@ -272,7 +272,7 @@ static inline struct team_port *team_get_port_by_index_rcu(struct team *team,
 	struct hlist_head *head = team_port_index_hash(team, port_index);
 
 	hlist_for_each_entry_rcu(port, head, hlist)
-		if (port->index == port_index)
+		if (READ_ONCE(port->index) == port_index)
 			return port;
 	return NULL;
 }

-- 
2.53.0.1185.g05d4b7b318-goog