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

Hangbin Liu
2025-01-09T08:37:35Z

On Thu, Jan 09, 2025 at 09:26:38AM +0800, Jianbo Liu wrote:
>
>
> On 1/8/2025 3:14 PM, Hangbin Liu wrote:
> > On Wed, Jan 08, 2025 at 11:40:05AM +0800, Jianbo Liu wrote:
> > >
> > >
> > > On 1/8/2025 10:46 AM, Hangbin Liu wrote:
> > > > On Mon, Jan 06, 2025 at 10:47:16AM +0000, Hangbin Liu wrote:
> > > > > On Thu, Jan 02, 2025 at 11:33:34AM +0800, Jianbo Liu wrote:
> > > > > > > > Re-locking doesn't look great, glancing at the code I don't see any
> > > > > > > > obvious better workarounds. Easiest fix would be to don't let the
> > > > > > > > drivers sleep in the callbacks and then we can go back to a spin lock.
> > > > > > > > Maybe nvidia people have better ideas, I'm not familiar with this
> > > > > > > > offload.
> > > > > > >
> > > > > > > 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:
> >
>
> Yes. Not feasible?
>
> > 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);
> >
> > Then why we need the spin lock in xfrm_state_delete?
> >
>
> No, we don't need. But I am trying to understand what you said in your last
> email about adding a new lock, or unlocking spin lock in

I *thought* we need the spin lock in xfrm_state_delete(). So to protect xfrm_state,
we need a new lock. Although it looks redundant. e.g.

int xfrm_state_delete(struct xfrm_state *x)
{
int err;

spin_lock_bh(&x->lock);
err = __xfrm_state_delete(x);
spin_unlock_bh(&x->lock);
if (err)
return err;

another_lock(&x->other_lock)
if (x->km.state == XFRM_STATE_DEAD) {
xfrm_dev_state_delete(x);
xfrm_state_put(x);
}
another_unlock(&x->other_lock)

return 0;
}
> bond_ipsec_del_sa(). Anything I missed?

The unlock spin lock in bond_ipsec_del_sa looks like
https://lore.kernel.org/netdev/Z1vfsAyuxcohT7th@fedora/

Thanks
Hangbin