[PATCH net-next 09/11] bridge: provide lockless access to p->port_id

[Eric Dumazet <edumazet@google.com>]

sysfs show_port_id() and BRCTL_GET_PORT_INFO need this.

This will be needed for upcoming RTNL avoidance in "ip link"
dumps (cf br_port_fill_attrs()).

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/bridge/br_ioctl.c    | 2 +-
 net/bridge/br_netlink.c  | 2 +-
 net/bridge/br_stp_if.c   | 4 ++--
 net/bridge/br_sysfs_if.c | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index 2be802991f70ab3ce48ade5da6d1488e072dbec6..a017374c6e659498d98c6af3f8d8e46a8b93570e 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -257,7 +257,7 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq,
 		memset(&p, 0, sizeof(struct __port_info));
 		memcpy(&p.designated_root, &pt->designated_root, 8);
 		memcpy(&p.designated_bridge, &pt->designated_bridge, 8);
-		p.port_id = pt->port_id;
+		p.port_id = READ_ONCE(pt->port_id);
 		p.designated_port = READ_ONCE(pt->designated_port);
 		p.path_cost = READ_ONCE(pt->path_cost);
 		p.designated_cost = READ_ONCE(pt->designated_cost);
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 30e253ca8d0b1ec9126e576629ade5211ab066ca..7b039994d6a2df00a2fc8ca50e45e7db4f392fa7 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -267,7 +267,7 @@ static int br_port_fill_attrs(struct sk_buff *skb,
 			READ_ONCE(p->designated_port)) ||
 	    nla_put_u16(skb, IFLA_BRPORT_DESIGNATED_COST,
 			READ_ONCE(p->designated_cost)) ||
-	    nla_put_u16(skb, IFLA_BRPORT_ID, p->port_id) ||
+	    nla_put_u16(skb, IFLA_BRPORT_ID, READ_ONCE(p->port_id)) ||
 	    nla_put_u16(skb, IFLA_BRPORT_NO, p->port_no) ||
 	    nla_put_u8(skb, IFLA_BRPORT_TOPOLOGY_CHANGE_ACK,
 		       p->topology_change_ack) ||
diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 3524bb7e87f0586774a883720be9fa8eb60f0370..8a418f6af423ccba88fae57d2254e35e1ae4a1a0 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -34,7 +34,7 @@ void br_init_port(struct net_bridge_port *p)
 {
 	int err;
 
-	p->port_id = br_make_port_id(p->priority, p->port_no);
+	WRITE_ONCE(p->port_id, br_make_port_id(p->priority, p->port_no));
 	br_become_designated_port(p);
 	br_set_state(p, BR_STATE_BLOCKING);
 	p->topology_change_ack = 0;
@@ -322,7 +322,7 @@ int br_stp_set_port_priority(struct net_bridge_port *p, unsigned long newprio)
 	if (br_is_designated_port(p))
 		WRITE_ONCE(p->designated_port, new_port_id);
 
-	p->port_id = new_port_id;
+	WRITE_ONCE(p->port_id, new_port_id);
 	WRITE_ONCE(p->priority, newprio);
 	if (!memcmp(&p->br->bridge_id, &p->designated_bridge, 8) &&
 	    p->port_id < p->designated_port) {
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index 7c55f78237d9e421ac9c3e64d71cc021ca75d1c7..af17f62e95aaff320f8407aa7b50244573ecdc00 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -123,7 +123,7 @@ static BRPORT_ATTR(designated_cost, 0444, show_designated_cost, NULL);
 
 static ssize_t show_port_id(struct net_bridge_port *p, char *buf)
 {
-	return sysfs_emit(buf, "0x%x\n", p->port_id);
+	return sysfs_emit(buf, "0x%x\n", READ_ONCE(p->port_id));
 }
 static BRPORT_ATTR(port_id, 0444, show_port_id, NULL);
 
-- 
2.54.0.669.g59709faab0-goog