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bridge: provide lockless access to p->path_cost

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Add READ_ONCE()/WRITE_ONCE() annotations around p->path_cost.

This is needed at least for sysfs show_path_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/20260604141343.2124500-6-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-06-04 14:13:37 +00:00 committed by Jakub Kicinski
parent 2013ebb9b3
commit f236240c9b
6 changed files with 16 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
net/bridge/br_if.c
View File

@ -78,7 +78,7 @@ void br_port_carrier_check(struct net_bridge_port *p, bool *notified)
if (!test_bit(BR_ADMIN_COST_BIT, &p->flags) &&
netif_running(dev) && netif_oper_up(dev))
p->path_cost = port_cost(dev);
WRITE_ONCE(p->path_cost, port_cost(dev));
*notified = false;
if (!netif_running(br->dev))

2
net/bridge/br_ioctl.c
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@ -259,7 +259,7 @@ int br_dev_siocdevprivate(struct net_device *dev, struct ifreq *rq,
memcpy(&p.designated_bridge, &pt->designated_bridge, 8);
p.port_id = pt->port_id;
p.designated_port = pt->designated_port;
p.path_cost = pt->path_cost;
p.path_cost = READ_ONCE(pt->path_cost);
p.designated_cost = pt->designated_cost;
p.state = pt->state;
p.top_change_ack = pt->topology_change_ack;

2
net/bridge/br_netlink.c
View File

@ -240,7 +240,7 @@ static int br_port_fill_attrs(struct sk_buff *skb,
if (nla_put_u8(skb, IFLA_BRPORT_STATE, p->state) ||
nla_put_u16(skb, IFLA_BRPORT_PRIORITY, p->priority) ||
nla_put_u32(skb, IFLA_BRPORT_COST, p->path_cost) ||
nla_put_u32(skb, IFLA_BRPORT_COST, READ_ONCE(p->path_cost)) ||
nla_put_u8(skb, IFLA_BRPORT_MODE, mode) ||
nla_put_u8(skb, IFLA_BRPORT_GUARD, !!(p->flags & BR_BPDU_GUARD)) ||
nla_put_u8(skb, IFLA_BRPORT_PROTECT,

17
net/bridge/br_stp.c
View File

@ -102,8 +102,9 @@ 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)
{
struct net_bridge *br;
u32 p_path_cost, rp_path_cost;
struct net_bridge_port *rp;
struct net_bridge *br;
int t;
br = p->br;
@ -125,11 +126,14 @@ static int br_should_become_root_port(const struct net_bridge_port *p,
else if (t > 0)
return 0;
if (p->designated_cost + p->path_cost <
rp->designated_cost + rp->path_cost)
p_path_cost = READ_ONCE(p->path_cost);
rp_path_cost = READ_ONCE(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);
@ -187,7 +191,8 @@ 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 + p->path_cost;
br->root_path_cost = p->designated_cost +
READ_ONCE(p->path_cost);
}
}

2
net/bridge/br_stp_if.c
View File

@ -341,7 +341,7 @@ int br_stp_set_path_cost(struct net_bridge_port *p, unsigned long path_cost)
return -ERANGE;
set_bit(BR_ADMIN_COST_BIT, &p->flags);
p->path_cost = path_cost;
WRITE_ONCE(p->path_cost, path_cost);
br_configuration_update(p->br);
br_port_state_selection(p->br);
return 0;

2
net/bridge/br_sysfs_if.c
View File

@ -83,7 +83,7 @@ static int store_flag(struct net_bridge_port *p, unsigned long v,
static ssize_t show_path_cost(struct net_bridge_port *p, char *buf)
{
return sysfs_emit(buf, "%d\n", p->path_cost);
return sysfs_emit(buf, "%d\n", READ_ONCE(p->path_cost));
}
static int store_path_cost(struct net_bridge_port *p, unsigned long v)