[PATCH v2 net-next 2/5] bridge: use atomic ops to read/change p->flags in br_netlink.c

[Eric Dumazet <edumazet@google.com>]

Change net/bridge/br_netlink.c to use atomic operations
to read/change bits in p->flags.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/bridge/br_netlink.c | 97 ++++++++++++++++++++++-------------------
 1 file changed, 52 insertions(+), 45 deletions(-)

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 7cb24de9c77d3d15892723f77288c27a15a6a0ad..12850f60bfcb418918508612070a6b0266ffbe6b 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -113,7 +113,7 @@ static size_t br_get_link_af_size_filtered(const struct net_device *dev,
 	num_vlan_infos = br_get_num_vlan_infos(vg, filter_mask);
 	rcu_read_unlock();
 
-	if (p && (p->flags & BR_VLAN_TUNNEL))
+	if (p && test_bit(BR_VLAN_TUNNEL_BIT, &p->flags))
 		vinfo_sz += br_get_vlan_tunnel_info_size(vg);
 
 	/* Each VLAN is returned in bridge_vlan_info along with flags */
@@ -823,7 +823,7 @@ static int br_afspec(struct net_bridge *br,
 		err = 0;
 		switch (nla_type(attr)) {
 		case IFLA_BRIDGE_VLAN_TUNNEL_INFO:
-			if (!p || !(p->flags & BR_VLAN_TUNNEL))
+			if (!p || !test_bit(BR_VLAN_TUNNEL_BIT, &p->flags))
 				return -EINVAL;
 			err = br_parse_vlan_tunnel_info(attr, &tinfo_curr);
 			if (err)
@@ -934,58 +934,64 @@ static int br_set_port_state(struct net_bridge_port *p, u8 state)
 }
 
 /* Set/clear or port flags based on attribute */
-static void br_set_port_flag(struct net_bridge_port *p, struct nlattr *tb[],
+static unsigned long br_set_port_flag(unsigned long flags, struct nlattr *tb[],
 			     int attrtype, unsigned long mask)
 {
-	if (!tb[attrtype])
-		return;
-
-	if (nla_get_u8(tb[attrtype]))
-		p->flags |= mask;
-	else
-		p->flags &= ~mask;
+	if (tb[attrtype]) {
+		if (nla_get_u8(tb[attrtype]))
+			flags |= mask;
+		else
+			flags &= ~mask;
+	}
+	return flags;
 }
 
 /* Process bridge protocol info on port */
 static int br_setport(struct net_bridge_port *p, struct nlattr *tb[],
 		      struct netlink_ext_ack *extack)
 {
-	unsigned long old_flags, changed_mask;
+	unsigned long old_flags, flags, changed_mask;
 	bool br_vlan_tunnel_old;
 	int err;
 
-	old_flags = p->flags;
+retry:
+	flags = old_flags = READ_ONCE(p->flags);
 	br_vlan_tunnel_old = (old_flags & BR_VLAN_TUNNEL) ? true : false;
 
-	br_set_port_flag(p, tb, IFLA_BRPORT_MODE, BR_HAIRPIN_MODE);
-	br_set_port_flag(p, tb, IFLA_BRPORT_GUARD, BR_BPDU_GUARD);
-	br_set_port_flag(p, tb, IFLA_BRPORT_FAST_LEAVE,
-			 BR_MULTICAST_FAST_LEAVE);
-	br_set_port_flag(p, tb, IFLA_BRPORT_PROTECT, BR_ROOT_BLOCK);
-	br_set_port_flag(p, tb, IFLA_BRPORT_LEARNING, BR_LEARNING);
-	br_set_port_flag(p, tb, IFLA_BRPORT_UNICAST_FLOOD, BR_FLOOD);
-	br_set_port_flag(p, tb, IFLA_BRPORT_MCAST_FLOOD, BR_MCAST_FLOOD);
-	br_set_port_flag(p, tb, IFLA_BRPORT_MCAST_TO_UCAST,
-			 BR_MULTICAST_TO_UNICAST);
-	br_set_port_flag(p, tb, IFLA_BRPORT_BCAST_FLOOD, BR_BCAST_FLOOD);
-	br_set_port_flag(p, tb, IFLA_BRPORT_PROXYARP, BR_PROXYARP);
-	br_set_port_flag(p, tb, IFLA_BRPORT_PROXYARP_WIFI, BR_PROXYARP_WIFI);
-	br_set_port_flag(p, tb, IFLA_BRPORT_VLAN_TUNNEL, BR_VLAN_TUNNEL);
-	br_set_port_flag(p, tb, IFLA_BRPORT_NEIGH_SUPPRESS, BR_NEIGH_SUPPRESS);
-	br_set_port_flag(p, tb, IFLA_BRPORT_ISOLATED, BR_ISOLATED);
-	br_set_port_flag(p, tb, IFLA_BRPORT_LOCKED, BR_PORT_LOCKED);
-	br_set_port_flag(p, tb, IFLA_BRPORT_MAB, BR_PORT_MAB);
-	br_set_port_flag(p, tb, IFLA_BRPORT_NEIGH_VLAN_SUPPRESS,
-			 BR_NEIGH_VLAN_SUPPRESS);
-	br_set_port_flag(p, tb, IFLA_BRPORT_NEIGH_FORWARD_GRAT,
-			 BR_NEIGH_FORWARD_GRAT);
-
-	if ((p->flags & BR_PORT_MAB) &&
-	    (!(p->flags & BR_PORT_LOCKED) || !(p->flags & BR_LEARNING))) {
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_MODE, BR_HAIRPIN_MODE);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_GUARD, BR_BPDU_GUARD);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_FAST_LEAVE,
+				 BR_MULTICAST_FAST_LEAVE);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_PROTECT, BR_ROOT_BLOCK);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_LEARNING, BR_LEARNING);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_UNICAST_FLOOD, BR_FLOOD);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_MCAST_FLOOD,
+				 BR_MCAST_FLOOD);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_MCAST_TO_UCAST,
+				 BR_MULTICAST_TO_UNICAST);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_BCAST_FLOOD,
+				 BR_BCAST_FLOOD);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_PROXYARP, BR_PROXYARP);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_PROXYARP_WIFI,
+				 BR_PROXYARP_WIFI);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_VLAN_TUNNEL,
+				 BR_VLAN_TUNNEL);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_NEIGH_SUPPRESS,
+				 BR_NEIGH_SUPPRESS);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_ISOLATED, BR_ISOLATED);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_LOCKED, BR_PORT_LOCKED);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_MAB, BR_PORT_MAB);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_NEIGH_VLAN_SUPPRESS,
+				 BR_NEIGH_VLAN_SUPPRESS);
+	flags = br_set_port_flag(flags, tb, IFLA_BRPORT_NEIGH_FORWARD_GRAT,
+				 BR_NEIGH_FORWARD_GRAT);
+
+	if ((flags & BR_PORT_MAB) &&
+	    (!(flags & BR_PORT_LOCKED) || !(flags & BR_LEARNING))) {
 		NL_SET_ERR_MSG(extack, "Bridge port must be locked and have learning enabled when MAB is enabled");
-		p->flags = old_flags;
 		return -EINVAL;
-	} else if (!(p->flags & BR_PORT_MAB) && (old_flags & BR_PORT_MAB)) {
+	}
+	if (!(flags & BR_PORT_MAB) && (old_flags & BR_PORT_MAB)) {
 		struct net_bridge_fdb_flush_desc desc = {
 			.flags = BIT(BR_FDB_LOCKED),
 			.flags_mask = BIT(BR_FDB_LOCKED),
@@ -995,15 +1001,16 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[],
 		br_fdb_flush(p->br, &desc);
 	}
 
-	changed_mask = old_flags ^ p->flags;
+	changed_mask = old_flags ^ flags;
 
-	err = br_switchdev_set_port_flag(p, p->flags, changed_mask, extack);
-	if (err) {
-		p->flags = old_flags;
+	err = br_switchdev_set_port_flag(p, flags, changed_mask, extack);
+	if (err)
 		return err;
-	}
 
-	if (br_vlan_tunnel_old && !(p->flags & BR_VLAN_TUNNEL))
+	if (cmpxchg(&p->flags, old_flags, flags) != old_flags)
+		goto retry;
+
+	if (br_vlan_tunnel_old && !(flags & BR_VLAN_TUNNEL))
 		nbp_vlan_tunnel_info_flush(p);
 
 	br_port_flags_change(p, changed_mask);
-- 
2.54.0.1099.g489fc7bff1-goog