Subject: Re: [PATCH net-next 3/3] bonding: no longer use RTNL in bonding_show_queue_id()

From: Jay Vosburgh <[email-masked]>
Date: Tue, 09 Apr 2024 13:39:33 -0700

Eric Dumazet <[email-masked]> wrote:

>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().

	This is combining two logical changes into one patch, isn't it?
The annotation change isn't part of what's stated in the Subject.

	-J

>Signed-off-by: Eric Dumazet <[email-masked]>
>---
> drivers/net/bonding/bond_main.c        |  2 +-
> drivers/net/bonding/bond_netlink.c     |  3 ++-
> drivers/net/bonding/bond_options.c     |  2 +-
> drivers/net/bonding/bond_procfs.c      |  2 +-
> drivers/net/bonding/bond_sysfs.c       | 10 +++++-----
> drivers/net/bonding/bond_sysfs_slave.c |  2 +-
> 6 files changed, 11 insertions(+), 10 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 08e9bdbf450afdc103931249259c58a08665dc02..b3a7d60c3a5ca60be1d9eed184ec1dad593a182b 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/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);
>diff --git a/drivers/net/bonding/bond_netlink.c b/drivers/net/bonding/bond_netlink.c
>index 29b4c3d1b9b6ff873fe067e80bedf7cb681d18f1..2a6a424806aa603ad8a00ca797e9e22d38bd0435 100644
>--- a/drivers/net/bonding/bond_netlink.c
>+++ b/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))
>diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
>index 4cdbc7e084f4b4cb3b150656aa765531806d8ad9..0cacd7027e352dbf3204d82b7ce1672469a186de 100644
>--- a/drivers/net/bonding/bond_options.c
>+++ b/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;
>diff --git a/drivers/net/bonding/bond_procfs.c b/drivers/net/bonding/bond_procfs.c
>index 43be458422b3f9448d96383b0fb140837562f446..7edf72ec816abd8b66917bdecd2c93d237629ffa 100644
>--- a/drivers/net/bonding/bond_procfs.c
>+++ b/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;
>diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
>index 75ee7ca369034ef6fa58fc9399b566dd7044fedc..1e13bb17051567e2b5d9451ceef47f2cf1a588ec 100644
>--- a/drivers/net/bonding/bond_sysfs.c
>+++ b/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;
> }
>diff --git a/drivers/net/bonding/bond_sysfs_slave.c b/drivers/net/bonding/bond_sysfs_slave.c
>index 313866f2c0e49ac96299ffea307b1613955713ec..36d0e8440b5b94464b3226ce1a04f32361de5aa6 100644
>--- a/drivers/net/bonding/bond_sysfs_slave.c
>+++ b/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);
> 
>-- 
>2.44.0.478.gd926399ef9-goog
>
>

---
	-Jay Vosburgh, [email-masked]