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

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Message-ID: <b39dfbee-dd80-48b2-b79c-29682269522a@nvidia.com>
Date: Thu, 9 Jan 2025 17:51:07 +0800
From: Jianbo Liu <jianbol@...dia.com>
To: Hangbin Liu <liuhangbin@...il.com>
CC: Jakub Kicinski <kuba@...nel.org>, <netdev@...r.kernel.org>, Jay Vosburgh
	<jv@...sburgh.net>, Andy Gospodarek <andy@...yhouse.net>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
	<pabeni@...hat.com>, Nikolay Aleksandrov <razor@...ckwall.org>, Simon Horman
	<horms@...nel.org>, Tariq Toukan <tariqt@...dia.com>, Andrew Lunn
	<andrew+netdev@...n.ch>, Shuah Khan <shuah@...nel.org>, Steffen Klassert
	<steffen.klassert@...unet.com>, Herbert Xu <herbert@...dor.apana.org.au>,
	Sabrina Dubroca <sd@...asysnail.net>, <linux-kselftest@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net 0/2] bond: fix xfrm offload feature during init



On 1/9/2025 4:37 PM, Hangbin Liu wrote:
> 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,

But not need in bond_ipsec_del_sa() because the state still hold by 
xfrm_state_hold(), right?

> 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