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

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Message-ID: <900054ae-be78-4d5e-aa5a-cb3ad91599e5@davidwei.uk>
Date: Sun, 21 Jul 2024 23:28:23 -0700
From: David Wei <dw@...idwei.uk>
To: Jay Vosburgh <jv@...sburgh.net>, netdev@...r.kernel.org
Cc: Andy Gospodarek <andy@...yhouse.net>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH RFC net-next] bonding: Remove support for use_carrier

On 2024-07-21 10:07, 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@...sburgh.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.

Net-next is closed until 28 July. Please resubmit then.