netdev - Re: [PATCH net-next 1/4] net: bonding: Notify ports about their initial state

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Date:   Thu, 19 Nov 2020 10:18:02 -0800
From:   Jay Vosburgh <jay.vosburgh@...onical.com>
To:     Tobias Waldekranz <tobias@...dekranz.com>
cc:     davem@...emloft.net, kuba@...nel.org, andrew@...n.ch,
        vivien.didelot@...il.com, f.fainelli@...il.com, olteanv@...il.com,
        vfalico@...il.com, andy@...yhouse.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/4] net: bonding: Notify ports about their initial state

Tobias Waldekranz <tobias@...dekranz.com> wrote:

>When creating a static bond (e.g. balance-xor), all ports will always
>be enabled. This is set, and the corresponding notification is sent
>out, before the port is linked to the bond upper.
>
>In the offloaded case, this ordering is hard to deal with.
>
>The lower will first see a notification that it can not associate with
>any bond. Then the bond is joined. After that point no more
>notifications are sent, so all ports remain disabled.

	Why are the notifications generated in __netdev_upper_dev_link
(via bond_master_upper_dev_link) not sufficient?

>This change simply sends an extra notification once the port has been
>linked to the upper to synchronize the initial state.
>
>Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
>---
> drivers/net/bonding/bond_main.c | 2 ++
> 1 file changed, 2 insertions(+)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 71c9677d135f..80c164198dcf 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -1897,6 +1897,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
> 		goto err_unregister;
> 	}
> 
>+	bond_lower_state_changed(new_slave);
>+
> 	res = bond_sysfs_slave_add(new_slave);
> 	if (res) {
> 		slave_dbg(bond_dev, slave_dev, "Error %d calling bond_sysfs_slave_add\n", res);

	Would it be better to add this call further down, after all
possible failures have been checked?  I.e., if this new call to
bond_lower_state_changed() completes, and then very soon afterwards the
upper is unlinked, could that cause any issues?

	-J

---
	-Jay Vosburgh, jay.vosburgh@...onical.com