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bridge: provide lockless access to p->designated_cost

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

This is needed at least for sysfs show_designated_cost(), 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>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260604141343.2124500-7-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-06-04 14:13:38 +00:00 committed by Jakub Kicinski
parent f236240c9b
commit 5deaf04951
4 changed files with 22 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
net/bridge/br_ioctl.c
View File

@ -260,7 +260,7 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq,
p.port_id = pt->port_id;
p.designated_port = pt->designated_port;
p.path_cost = READ_ONCE(pt->path_cost);
p.designated_cost = pt->designated_cost;
p.designated_cost = READ_ONCE(pt->designated_cost);
p.state = pt->state;
p.top_change_ack = pt->topology_change_ack;
p.config_pending = pt->config_pending;

3
net/bridge/br_netlink.c
View File

@ -264,7 +264,8 @@ static int br_port_fill_attrs(struct sk_buff *skb,
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_COST, p->designated_cost) ||
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_NO, p->port_no) ||
nla_put_u8(skb, IFLA_BRPORT_TOPOLOGY_CHANGE_ACK,

30
net/bridge/br_stp.c
View File

@ -102,7 +102,7 @@ struct net_bridge_port *br_get_port(struct net_bridge *br, u16 port_no)
static int br_should_become_root_port(const struct net_bridge_port *p,
u16 root_port)
{
u32 p_path_cost, rp_path_cost;
u32 p_path_cost, rp_path_cost, p_designated_cost, rp_designated_cost;
struct net_bridge_port *rp;
struct net_bridge *br;
int t;
@ -128,12 +128,14 @@ static int br_should_become_root_port(const struct net_bridge_port *p,
p_path_cost = READ_ONCE(p->path_cost);
rp_path_cost = READ_ONCE(rp->path_cost);
p_designated_cost = READ_ONCE(p->designated_cost);
rp_designated_cost = READ_ONCE(rp->designated_cost);
if (p->designated_cost + p_path_cost <
rp->designated_cost + rp_path_cost)
if (p_designated_cost + p_path_cost <
rp_designated_cost + rp_path_cost)
return 1;
else if (p->designated_cost + p_path_cost >
rp->designated_cost + rp_path_cost)
else if (p_designated_cost + p_path_cost >
rp_designated_cost + rp_path_cost)
return 0;
t = memcmp(&p->designated_bridge, &rp->designated_bridge, 8);
@ -191,7 +193,7 @@ static void br_root_selection(struct net_bridge *br)
} else {
p = br_get_port(br, root_port);
br->designated_root = p->designated_root;
br->root_path_cost = p->designated_cost +
br->root_path_cost = READ_ONCE(p->designated_cost) +
READ_ONCE(p->path_cost);
}
}
@ -257,7 +259,7 @@ static void br_record_config_information(struct net_bridge_port *p,
const struct br_config_bpdu *bpdu)
{
p->designated_root = bpdu->root;
p->designated_cost = bpdu->root_path_cost;
WRITE_ONCE(p->designated_cost, bpdu->root_path_cost);
p->designated_bridge = bpdu->bridge_id;
p->designated_port = bpdu->port_id;
p->designated_age = jiffies - bpdu->message_age;
@ -293,6 +295,7 @@ void br_transmit_tcn(struct net_bridge *br)
static int br_should_become_designated_port(const struct net_bridge_port *p)
{
struct net_bridge *br;
u32 p_designated_cost;
int t;
br = p->br;
@ -302,9 +305,10 @@ static int br_should_become_designated_port(const struct net_bridge_port *p)
if (memcmp(&p->designated_root, &br->designated_root, 8))
return 1;
if (br->root_path_cost < p->designated_cost)
p_designated_cost = READ_ONCE(p->designated_cost);
if (br->root_path_cost < p_designated_cost)
return 1;
else if (br->root_path_cost > p->designated_cost)
else if (br->root_path_cost > p_designated_cost)
return 0;
t = memcmp(&br->bridge_id, &p->designated_bridge, 8);
@ -336,6 +340,7 @@ static void br_designated_port_selection(struct net_bridge *br)
static int br_supersedes_port_info(const struct net_bridge_port *p,
const struct br_config_bpdu *bpdu)
{
u32 p_designated_cost;
int t;
t = memcmp(&bpdu->root, &p->designated_root, 8);
@ -344,9 +349,10 @@ static int br_supersedes_port_info(const struct net_bridge_port *p,
else if (t > 0)
return 0;
if (bpdu->root_path_cost < p->designated_cost)
p_designated_cost = READ_ONCE(p->designated_cost);
if (bpdu->root_path_cost < p_designated_cost)
return 1;
else if (bpdu->root_path_cost > p->designated_cost)
else if (bpdu->root_path_cost > p_designated_cost)
return 0;
t = memcmp(&bpdu->bridge_id, &p->designated_bridge, 8);
@ -426,7 +432,7 @@ void br_become_designated_port(struct net_bridge_port *p)
br = p->br;
p->designated_root = br->designated_root;
p->designated_cost = br->root_path_cost;
WRITE_ONCE(p->designated_cost, br->root_path_cost);
p->designated_bridge = br->bridge_id;
p->designated_port = p->port_id;
}

2
net/bridge/br_sysfs_if.c
View File

@ -135,7 +135,7 @@ static BRPORT_ATTR(designated_port, 0444, show_designated_port, NULL);
static ssize_t show_designated_cost(struct net_bridge_port *p, char *buf)
{
return sysfs_emit(buf, "%d\n", p->designated_cost);
return sysfs_emit(buf, "%d\n", READ_ONCE(p->designated_cost));
}
static BRPORT_ATTR(designated_cost, 0444, show_designated_cost, NULL);