bonding: no longer use RTNL in bonding_show_queue_id()

Annotate lockless reads of slave->queue_id.

Annotate writes of slave->queue_id.

Switch bonding_show_queue_id() to rcu_read_lock()
and bond_for_each_slave_rcu().
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Link: https://lore.kernel.org/r/20240408190437.2214473-4-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/bonding/bond_main.c

@@ -5245,7 +5245,7 @@ static inline int bond_slave_override(struct bonding *bond,
 
 	/* Find out if any slaves have the same mapping as this skb. */
 	bond_for_each_slave_rcu(bond, slave, iter) {
-		if (slave->queue_id == skb_get_queue_mapping(skb)) {
+		if (READ_ONCE(slave->queue_id) == skb_get_queue_mapping(skb)) {
 			if (bond_slave_is_up(slave) &&
 			    slave->link == BOND_LINK_UP) {
 				bond_dev_queue_xmit(bond, skb, slave->dev);

drivers/net/bonding/bond_netlink.c

@@ -51,7 +51,8 @@ static int bond_fill_slave_info(struct sk_buff *skb,
 		    slave_dev->addr_len, slave->perm_hwaddr))
 		goto nla_put_failure;
 
-	if (nla_put_u16(skb, IFLA_BOND_SLAVE_QUEUE_ID, slave->queue_id))
+	if (nla_put_u16(skb, IFLA_BOND_SLAVE_QUEUE_ID,
+			READ_ONCE(slave->queue_id)))
 		goto nla_put_failure;
 
 	if (nla_put_s32(skb, IFLA_BOND_SLAVE_PRIO, slave->prio))

drivers/net/bonding/bond_options.c

@@ -1589,7 +1589,7 @@ static int bond_option_queue_id_set(struct bonding *bond,
 		goto err_no_cmd;
 
 	/* Actually set the qids for the slave */
-	update_slave->queue_id = qid;
+	WRITE_ONCE(update_slave->queue_id, qid);
 
 out:
 	return ret;

drivers/net/bonding/bond_procfs.c

@@ -209,7 +209,7 @@ static void bond_info_show_slave(struct seq_file *seq,
 
 	seq_printf(seq, "Permanent HW addr: %*phC\n",
 		   slave->dev->addr_len, slave->perm_hwaddr);
-	seq_printf(seq, "Slave queue ID: %d\n", slave->queue_id);
+	seq_printf(seq, "Slave queue ID: %d\n", READ_ONCE(slave->queue_id));
 
 	if (BOND_MODE(bond) == BOND_MODE_8023AD) {
 		const struct port *port = &SLAVE_AD_INFO(slave)->port;

drivers/net/bonding/bond_sysfs.c

@@ -625,10 +625,9 @@ static ssize_t bonding_show_queue_id(struct device *d,
 	struct slave *slave;
 	int res = 0;
 
-	if (!rtnl_trylock())
-		return restart_syscall();
+	rcu_read_lock();
 
-	bond_for_each_slave(bond, slave, iter) {
+	bond_for_each_slave_rcu(bond, slave, iter) {
 		if (res > (PAGE_SIZE - IFNAMSIZ - 6)) {
 			/* not enough space for another interface_name:queue_id pair */
 			if ((PAGE_SIZE - res) > 10)
@@ -637,12 +636,13 @@ static ssize_t bonding_show_queue_id(struct device *d,
 			break;
 		}
 		res += sysfs_emit_at(buf, res, "%s:%d ",
-				     slave->dev->name, slave->queue_id);
+				     slave->dev->name,
+				     READ_ONCE(slave->queue_id));
 	}
 	if (res)
 		buf[res-1] = '\n'; /* eat the leftover space */
 
-	rtnl_unlock();
+	rcu_read_unlock();
 
 	return res;
 }

drivers/net/bonding/bond_sysfs_slave.c

@@ -53,7 +53,7 @@ static SLAVE_ATTR_RO(perm_hwaddr);
 
 static ssize_t queue_id_show(struct slave *slave, char *buf)
 {
-	return sysfs_emit(buf, "%d\n", slave->queue_id);
+	return sysfs_emit(buf, "%d\n", READ_ONCE(slave->queue_id));
 }
 static SLAVE_ATTR_RO(queue_id);