netdev - Re: [PATCH net] net: drop secpath extension before skb deferral free

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Message-ID: <20240526105713.GB96190@unreal>
Date: Sun, 26 May 2024 13:57:13 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Steffen Klassert <steffen.klassert@...unet.com>
Cc: Jianbo Liu <jianbol@...dia.com>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"fw@...len.de" <fw@...len.de>
Subject: Re: [PATCH net] net: drop secpath extension before skb deferral free

On Thu, May 23, 2024 at 08:44:56AM +0200, Steffen Klassert wrote:
> On Thu, May 23, 2024 at 02:22:38AM +0000, Jianbo Liu wrote:
> > On Wed, 2024-05-22 at 11:34 +0200, Steffen Klassert wrote:
> > > 
> > > Maybe we should directly remove the device from the xfrm_state
> > > when the decice goes down, this should catch all the cases.
> > > 
> > > I think about something like this (untested) patch:
> > > 
> > > diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
> > > index 0c306473a79d..ba402275ab57 100644
> > > --- a/net/xfrm/xfrm_state.c
> > > +++ b/net/xfrm/xfrm_state.c
> > > @@ -867,7 +867,11 @@ int xfrm_dev_state_flush(struct net *net, struct
> > > net_device *dev, bool task_vali
> > >                                 xfrm_state_hold(x);
> > >                                 spin_unlock_bh(&net-
> > > >xfrm.xfrm_state_lock);
> > >  
> > > -                               err = xfrm_state_delete(x);
> > > +                               spin_lock_bh(&x->lock);
> > > +                               err = __xfrm_state_delete(x);
> > > +                               xfrm_dev_state_free(x);
> > > +                               spin_unlock_bh(&x->lock);
> > > +
> > >                                 xfrm_audit_state_delete(x, err ? 0 :
> > > 1,
> > >                                                         task_valid);
> > >                                 xfrm_state_put(x);
> > > 
> > > The secpath is still attached to all skbs, but the hang on device
> > > unregister should go away.
> > 
> > It didn't fix the issue.
> 
> Do you have a backtrace of the ref_tracker?
> 
> Is that with packet offload?

We saw same failure with crypto and packet offloads.

> 
> Looks like we need to remove the device from the xfrm_policy
> too if packet offload is used.

When we debugged it, we found that this line [1] was responsible for
elevated reference count. XFRM policy cleaned properly.

Thanks

[1] https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.c#L332

>