[PATCH net-next 07/11] bridge: provide lockless access to p->designated_port

[Eric Dumazet <edumazet@google.com>]

Add READ_ONCE()/WRITE_ONCE() annotations around p->designated_cost

This is needed at least for sysfs show_designated_port(), BRCTL_GET_PORT_INFO
and 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  | 3 ++-
 net/bridge/br_stp.c      | 4 ++--
 net/bridge/br_stp_if.c   | 2 +-
 net/bridge/br_sysfs_if.c | 2 +-
 5 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index a507c7b369ac49803019cdca7836c7fb9ef4459e..2be802991f70ab3ce48ade5da6d1488e072dbec6 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -258,7 +258,7 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq,
 		memcpy(&p.designated_root, &pt->designated_root, 8);
 		memcpy(&p.designated_bridge, &pt->designated_bridge, 8);
 		p.port_id = pt->port_id;
-		p.designated_port = pt->designated_port;
+		p.designated_port = READ_ONCE(pt->designated_port);
 		p.path_cost = READ_ONCE(pt->path_cost);
 		p.designated_cost = READ_ONCE(pt->designated_cost);
 		p.state = pt->state;
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 153e1cb0fbb6ea9f65933d884b9a78f5446d0de6..3c10125cfa6e703dec609a63940632b9b206d132 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -263,7 +263,8 @@ static int br_port_fill_attrs(struct sk_buff *skb,
 		    &p->designated_root) ||
 	    nla_put(skb, IFLA_BRPORT_BRIDGE_ID, sizeof(struct ifla_bridge_id),
 		    &p->designated_bridge) ||
-	    nla_put_u16(skb, IFLA_BRPORT_DESIGNATED_PORT, p->designated_port) ||
+	    nla_put_u16(skb, IFLA_BRPORT_DESIGNATED_PORT,
+			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) ||
diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index 62dcac1a181c829e2736d7ab8679c870ee676a71..4c364a7f0f53f4f9360887b93bfbc592c738e311 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -256,7 +256,7 @@ static void br_record_config_information(struct net_bridge_port *p,
 	p->designated_root = bpdu->root;
 	WRITE_ONCE(p->designated_cost, bpdu->root_path_cost);
 	p->designated_bridge = bpdu->bridge_id;
-	p->designated_port = bpdu->port_id;
+	WRITE_ONCE(p->designated_port, bpdu->port_id);
 	p->designated_age = jiffies - bpdu->message_age;
 
 	mod_timer(&p->message_age_timer, jiffies
@@ -427,7 +427,7 @@ void br_become_designated_port(struct net_bridge_port *p)
 	p->designated_root = br->designated_root;
 	WRITE_ONCE(p->designated_cost, br->root_path_cost);
 	p->designated_bridge = br->bridge_id;
-	p->designated_port = p->port_id;
+	WRITE_ONCE(p->designated_port, p->port_id);
 }
 
 
diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index e5d43492d2dcf0615ee984bc190d7ce2264aaab0..7b0d1a334785047905a00694fd65e3212b160e5d 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -320,7 +320,7 @@ int br_stp_set_port_priority(struct net_bridge_port *p, unsigned long newprio)
 
 	new_port_id = br_make_port_id(newprio, p->port_no);
 	if (br_is_designated_port(p))
-		p->designated_port = new_port_id;
+		WRITE_ONCE(p->designated_port, new_port_id);
 
 	p->port_id = new_port_id;
 	p->priority = newprio;
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index 9d560482e558aa1ef4d2f583373f15ae5db8a0f0..23ea003d72f413b1164496c3055832ab49197d4d 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -111,7 +111,7 @@ static BRPORT_ATTR(designated_bridge, 0444, show_designated_bridge, NULL);
 
 static ssize_t show_designated_port(struct net_bridge_port *p, char *buf)
 {
-	return sysfs_emit(buf, "%d\n", p->designated_port);
+	return sysfs_emit(buf, "%d\n", READ_ONCE(p->designated_port));
 }
 static BRPORT_ATTR(designated_port, 0444, show_designated_port, NULL);
 
-- 
2.54.0.669.g59709faab0-goog