Subject: Re: [PATCH net 0/2] bond: fix xfrm offload feature during init

From: Hangbin Liu <[email-masked]>
Date: Wed, 15 Jan 2025 09:19:33 +0000

On Wed, Jan 08, 2025 at 07:15:00AM +0000, Hangbin Liu wrote:
> > > > > > I don't know how to disable bonding sleeping since we use mutex_lock now.
> > > > > > Hi Jianbo, do you have any idea?
> > > > > > 
> > > > > 
> > > > > I think we should allow drivers to sleep in the callbacks. So, maybe it's
> > > > > better to move driver's xdo_dev_state_delete out of state's spin lock.
> > > > 
> > > > I just check the code, xfrm_dev_state_delete() and later
> > > > dev->xfrmdev_ops->xdo_dev_state_delete(x) have too many xfrm_state x
> > > > checks. Can we really move it out of spin lock from xfrm_state_delete()
> > > 
> > > I tried to move the mutex lock code to a work queue, but found we need to
> > > check (ipsec->xs == xs) in bonding. So we still need xfrm_state x during bond
> > 
> > Maybe I miss something, but why need to hold spin lock. You can keep xfrm
> > state by its refcnt.
> 
> Do you mean move the xfrm_dev_state_delete() out of spin lock directly like:
> 
> diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
> index 67ca7ac955a3..6881ddeb4360 100644
> --- a/net/xfrm/xfrm_state.c
> +++ b/net/xfrm/xfrm_state.c
> @@ -766,13 +766,6 @@ int __xfrm_state_delete(struct xfrm_state *x)
>  		if (x->encap_sk)
>  			sock_put(rcu_dereference_raw(x->encap_sk));
>  
> -		xfrm_dev_state_delete(x);
> -
> -		/* All xfrm_state objects are created by xfrm_state_alloc.
> -		 * The xfrm_state_alloc call gives a reference, and that
> -		 * is what we are dropping here.
> -		 */
> -		xfrm_state_put(x);
>  		err = 0;
>  	}
>  
> @@ -787,8 +780,20 @@ int xfrm_state_delete(struct xfrm_state *x)
>  	spin_lock_bh(&x->lock);
>  	err = __xfrm_state_delete(x);
>  	spin_unlock_bh(&x->lock);
> +	if (err)
> +		return err;
>  
> -	return err;
> +	if (x->km.state == XFRM_STATE_DEAD) {
> +		xfrm_dev_state_delete(x);
> +
> +		/* All xfrm_state objects are created by xfrm_state_alloc.
> +		 * The xfrm_state_alloc call gives a reference, and that
> +		 * is what we are dropping here.
> +		 */
> +		xfrm_state_put(x);
> +	}
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL(xfrm_state_delete);
>  

Hi Jianbo,

I talked with Sabrina and it looks we can't simply do this. Because both
xfrm_add_sa_expire() and xfrm_timer_handler() calling __xfrm_state_delete() under
spin lock. If we move the xfrm_dev_state_delete() out of __xfrm_state_delete(),
all the places need to be handled correctly.

At the same time xfrm_timer_handler() calling xfrm_dev_state_update_stats before
__xfrm_state_delete(). Should we also take care of it to make sure the state
change and delete are called at the same time?

Hi Steffen, do you have any comments?

Thanks
Hangbin