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

From: Hangbin Liu <[email-masked]>
Date: Wed, 8 Jan 2025 07:14:50 +0000

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:

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?

Hangbin