netdev - RE: [PATCH net] netdev: increment TSO only if TSO is not enabled on any slave device

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Message-ID: <fe236a552f594780a4b2ead63b4bc329@hygon.cn>
Date: Tue, 23 Dec 2025 12:20:43 +0000
From: Zhud <zhud@...on.cn>
To: Paolo Abeni <pabeni@...hat.com>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "horms@...nel.org" <horms@...nel.org>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
CC: Jing Li <lijing@...on.cn>, Zhiwei Ying <yingzhiwei@...on.cn>
Subject: RE: [PATCH net] netdev: increment TSO only if TSO is not enabled on
 any slave device


> On 12/16/25 9:52 AM, Di Zhu wrote:
> > Unconditionally increment the TSO flag has a side effect: it will also
> 
> This changelog is IMHO quite confusing. The code does not 'increment TSO'. Instead
> it increments the features set to include ALL_TSO.
> 
> Please reword the changelog accordingly.
> 
> > directly clear the flags in NETIF_F_ALL_FOR_ALL on the master device,
> > which can cause issues such as the inability to enable the nocache
> > copy feature on the bonding network card.
> 
> bonding network card -> bonding driver.
> 
> > So, when at least one slave device's TSO is enabled, there is no need
> > to explicitly increment the TSO flag to the master device.
> >
> > Fixes: b0ce3508b25e ("bonding: allow TSO being set on bonding master")
> > Signed-off-by: Di Zhu <zhud@...on.cn>
> > ---
> >  include/linux/netdevice.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index bf99fe8622da..2aca39f7f9e1 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -5322,7 +5322,8 @@ netdev_features_t
> > netdev_increment_features(netdev_features_t all,  static inline
> netdev_features_t netdev_add_tso_features(netdev_features_t features,
> >  							netdev_features_t mask)
> >  {
> > -	return netdev_increment_features(features, NETIF_F_ALL_TSO, mask);
> > +	return (features & NETIF_F_ALL_TSO) ? features :
> > +		netdev_increment_features(features, NETIF_F_ALL_TSO, mask);
> 
> NETIF_F_ALL_TSO is not a single bit, but a (later large) bit mask; the above will yield
> incorrect result when:
> 
> 	features & NETIF_F_ALL_TSO != NETIF_F_ALL_TSO

Yes, it is indeed necessary to set all tso flags to avoid GSO at the bonding layer.
I will revise the code and its related changlong, thanks.

> 
> /P
>