netdev - Re: [PATCH net-next 1/3] bonding: no longer use RTNL in bonding_show

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Message-ID: <17332.1712695034@famine>
Date: Tue, 09 Apr 2024 13:37:14 -0700
From: Jay Vosburgh <jay.vosburgh@...onical.com>
To: Eric Dumazet <edumazet@...gle.com>
cc: "David S . Miller" <davem@...emloft.net>,
    Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
    Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org,
    eric.dumazet@...il.com
Subject: Re: [PATCH net-next 1/3] bonding: no longer use RTNL in bonding_show_bonds()

Eric Dumazet <edumazet@...gle.com> wrote:

>netdev structures are already RCU protected.
>
>Change bond_init() and bond_uninit() to use RCU
>enabled list_add_tail_rcu() and list_del_rcu().
>
>Then bonding_show_bonds() can use rcu_read_lock()
>while iterating through bn->dev_list.
>
>Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Acked-by: Jay Vosburgh <jay.vosburgh@...onical.com>


>---
> drivers/net/bonding/bond_main.c  | 4 ++--
> drivers/net/bonding/bond_sysfs.c | 8 ++++----
> 2 files changed, 6 insertions(+), 6 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index c9f0415f780ab0a9ecb26424795695eff951421a..08e9bdbf450afdc103931249259c58a08665dc02 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -5933,7 +5933,7 @@ static void bond_uninit(struct net_device *bond_dev)
> 
> 	bond_set_slave_arr(bond, NULL, NULL);
> 
>-	list_del(&bond->bond_list);
>+	list_del_rcu(&bond->bond_list);
> 
> 	bond_debug_unregister(bond);
> }
>@@ -6347,7 +6347,7 @@ static int bond_init(struct net_device *bond_dev)
> 	spin_lock_init(&bond->stats_lock);
> 	netdev_lockdep_set_classes(bond_dev);
> 
>-	list_add_tail(&bond->bond_list, &bn->dev_list);
>+	list_add_tail_rcu(&bond->bond_list, &bn->dev_list);
> 
> 	bond_prepare_sysfs_group(bond);
> 
>diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
>index 2805135a7205ba444ccaf412df33f621f55a729a..9132033f85fb0e33093e97c55f885a997c95cb4a 100644
>--- a/drivers/net/bonding/bond_sysfs.c
>+++ b/drivers/net/bonding/bond_sysfs.c
>@@ -37,12 +37,12 @@ static ssize_t bonding_show_bonds(const struct class *cls,
> {
> 	const struct bond_net *bn =
> 		container_of_const(attr, struct bond_net, class_attr_bonding_masters);
>-	int res = 0;
> 	struct bonding *bond;
>+	int res = 0;
> 
>-	rtnl_lock();
>+	rcu_read_lock();
> 
>-	list_for_each_entry(bond, &bn->dev_list, bond_list) {
>+	list_for_each_entry_rcu(bond, &bn->dev_list, bond_list) {
> 		if (res > (PAGE_SIZE - IFNAMSIZ)) {
> 			/* not enough space for another interface name */
> 			if ((PAGE_SIZE - res) > 10)
>@@ -55,7 +55,7 @@ static ssize_t bonding_show_bonds(const struct class *cls,
> 	if (res)
> 		buf[res-1] = '\n'; /* eat the leftover space */
> 
>-	rtnl_unlock();
>+	rcu_read_unlock();
> 	return res;
> }
> 
>-- 
>2.44.0.478.gd926399ef9-goog
>
>