Re: [PATCH net-next] bonding: Remove support for use_carrier = 0

[Stanislav Fomichev <stfomichev@gmail.com>]

On 06/16, Jay Vosburgh wrote:
> 	 Remove the ability to disable use_carrier in bonding, and remove
> all code related to the old link state check that utilizes ethtool or
> ioctl to determine the link state of an interface in a bond.
> 
> 	To avoid acquiring RTNL many times per second, bonding's miimon
> link monitor inspects link state under RCU, but not under RTNL.  However,
> ethtool implementations in drivers may sleep, and therefore the ethtool or
> ioctl strategy is unsuitable for use with calls into driver ethtool
> functions.
> 
> 	The use_carrier option was introduced in 2003, to provide
> backwards compatibility for network device drivers that did not support
> the then-new netif_carrier_ok/on/off system.  Today, device drivers are
> expected to support netif_carrier_*, and the use_carrier backwards
> compatibility logic is no longer necessary.
> 
> 	Bonding now always behaves as if use_carrier=1, which relies on
> netif_carrier_ok() to determine the link state of interfaces.  This has
> been the default setting for use_carrier since its introduction.  For
> backwards compatibility, the option itself remains, but may only be set to
> 1, and queries will always return 1.
> 
> Reported-by: syzbot+b8c48ea38ca27d150063@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=b8c48ea38ca27d150063
> Link: https://lore.kernel.org/lkml/000000000000eb54bf061cfd666a@google.com/
> Link: https://lore.kernel.org/netdev/20240718122017.d2e33aaac43a.I10ab9c9ded97163aef4e4de10985cd8f7de60d28@changeid/
> Link: http://lore.kernel.org/netdev/aEt6LvBMwUMxmUyx@mini-arch
> Signed-off-by: Jay Vosburgh <jv@jvosburgh.net>

Acked-by: Stanislav Fomichev <sdf@fomichev.me>

Maybe better to target 'net' with the following?
Fixes: f7a11cba0ed7 ("bonding: hold ops lock around get_link")