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

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Message-ID: <e01bae5f-30b5-4ec4-8c4b-5c133dd4552a@nvidia.com>
Date: Thu, 9 Jan 2025 09:26:38 +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 1/8/2025 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 
bond_ipsec_del_sa(). Anything I missed?

Thanks!
Jianbo