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

[Hangbin Liu <liuhangbin@gmail.com>]

On Sun, Jul 21, 2024 at 10:07:52AM -0700, Jay Vosburgh wrote:
> 	Remove the implementation of use_carrier, the link monitoring
> method that utilizes ethtool or ioctl to determine the link state of an
> interface in a bond.  The ability to set or query the use_carrier option
> remains, but bonding now always behaves as if use_carrier=1, which
> relies on netif_carrier_ok() to determine the link state of interfaces.
> 
> 	To avoid acquiring RTNL many times per second, bonding inspects
> link state under RCU, but not under RTNL.  However, ethtool
> implementations in drivers may sleep, and therefore this 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.  Device drivers are now
> expected to support netif_carrier_*, and the use_carrier backwards
> compatibility logic is no longer necessary.
> 
> Link: https://lore.kernel.org/lkml/000000000000eb54bf061cfd666a@google.com/
> Link: https://lore.kernel.org/netdev/20240718122017.d2e33aaac43a.I10ab9c9ded97163aef4e4de10985cd8f7de60d28@changeid/
> Signed-off-by: Jay Vosburgh <jv@jvosburgh.net>
> 
> ---
> 
> 	I've done some sniff testing and this seems to behave as
> expected, except that writing 0 to the sysfs use_carrier fails.  Netlink
> permits setting use_carrier to any value but always returns 1; sysfs and
> netlink should behave consistently.
> 
>  drivers/net/bonding/bond_main.c    | 107 +----------------------------
>  drivers/net/bonding/bond_netlink.c |  11 +--
>  drivers/net/bonding/bond_options.c |  13 +---
>  drivers/net/bonding/bond_sysfs.c   |   6 +-
>  include/net/bonding.h              |   1 -
>  5 files changed, 7 insertions(+), 131 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_netlink.c b/drivers/net/bonding/bond_netlink.c
> index 2a6a424806aa..e35433cd76b1 100644
> --- a/drivers/net/bonding/bond_netlink.c
> +++ b/drivers/net/bonding/bond_netlink.c
> @@ -257,15 +257,6 @@ static int bond_changelink(struct net_device *bond_dev, struct nlattr *tb[],
>  		if (err)
>  			return err;
>  	}
> -	if (data[IFLA_BOND_USE_CARRIER]) {
> -		int use_carrier = nla_get_u8(data[IFLA_BOND_USE_CARRIER]);
> -
> -		bond_opt_initval(&newval, use_carrier);
> -		err = __bond_opt_set(bond, BOND_OPT_USE_CARRIER, &newval,
> -				     data[IFLA_BOND_USE_CARRIER], extack);
> -		if (err)
> -			return err;
> -	}

I'm not sure if we should return a warn/error if user want to set this.

BTW, the document also need update.

Others looks good to me.

Thanks
Hangbin