[PATCH net-next] net: sched: ingress: set 'unlocked' flag for Qdisc ops

[PATCH net-next] net: sched: ingress: set 'unlocked' flag for Qdisc ops

[Vlad Buslov]

To remove rtnl lock dependency in tc filter update API when using ingress
Qdisc, set QDISC_CLASS_OPS_DOIT_UNLOCKED flag in ingress Qdisc_class_ops.

Ingress Qdisc ops don't require any modifications to be used without rtnl
lock on tc filter update path. Ingress implementation never changes its
q->block and only releases it when Qdisc is being destroyed. This means it
is enough for RTM_{NEWTFILTER|DELTFILTER|GETTFILTER} message handlers to
hold ingress Qdisc reference while using it without relying on rtnl lock
protection. Unlocked Qdisc ops support is already implemented in filter
update path by unlocked cls API patch set.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
---
 net/sched/sch_ingress.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
index 0f65f617756b..d5382554e281 100644
--- a/net/sched/sch_ingress.c
+++ b/net/sched/sch_ingress.c
@@ -114,6 +114,7 @@ static int ingress_dump(struct Qdisc *sch, struct sk_buff *skb)
 }
 
 static const struct Qdisc_class_ops ingress_class_ops = {
+	.flags		=	QDISC_CLASS_OPS_DOIT_UNLOCKED,
 	.leaf		=	ingress_leaf,
 	.find		=	ingress_find,
 	.walk		=	ingress_walk,
-- 
2.21.0

Re: [PATCH net-next] net: sched: ingress: set 'unlocked' flag for Qdisc ops

[David Miller]

From: Vlad Buslov <vladbu@mellanox.com>
Date: Wed, 12 Jun 2019 10:14:35 +0300

> To remove rtnl lock dependency in tc filter update API when using ingress
> Qdisc, set QDISC_CLASS_OPS_DOIT_UNLOCKED flag in ingress Qdisc_class_ops.
> 
> Ingress Qdisc ops don't require any modifications to be used without rtnl
> lock on tc filter update path. Ingress implementation never changes its
> q->block and only releases it when Qdisc is being destroyed. This means it
> is enough for RTM_{NEWTFILTER|DELTFILTER|GETTFILTER} message handlers to
> hold ingress Qdisc reference while using it without relying on rtnl lock
> protection. Unlocked Qdisc ops support is already implemented in filter
> update path by unlocked cls API patch set.
> 
> Signed-off-by: Vlad Buslov <vladbu@mellanox.com>

Applied.

Re: [PATCH net-next] net: sched: ingress: set 'unlocked' flag for Qdisc ops

[Daniel Borkmann]

On 06/12/2019 09:14 AM, Vlad Buslov wrote:
> To remove rtnl lock dependency in tc filter update API when using ingress
> Qdisc, set QDISC_CLASS_OPS_DOIT_UNLOCKED flag in ingress Qdisc_class_ops.
> 
> Ingress Qdisc ops don't require any modifications to be used without rtnl
> lock on tc filter update path. Ingress implementation never changes its
> q->block and only releases it when Qdisc is being destroyed. This means it
> is enough for RTM_{NEWTFILTER|DELTFILTER|GETTFILTER} message handlers to
> hold ingress Qdisc reference while using it without relying on rtnl lock
> protection. Unlocked Qdisc ops support is already implemented in filter
> update path by unlocked cls API patch set.
> 
> Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
> ---
>  net/sched/sch_ingress.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
> index 0f65f617756b..d5382554e281 100644
> --- a/net/sched/sch_ingress.c
> +++ b/net/sched/sch_ingress.c
> @@ -114,6 +114,7 @@ static int ingress_dump(struct Qdisc *sch, struct sk_buff *skb)
>  }
>  
>  static const struct Qdisc_class_ops ingress_class_ops = {
> +	.flags		=	QDISC_CLASS_OPS_DOIT_UNLOCKED,
>  	.leaf		=	ingress_leaf,
>  	.find		=	ingress_find,
>  	.walk		=	ingress_walk,
> 

Vlad, why is clsact_class_ops not updated here? Please elaborate!

Re: [PATCH net-next] net: sched: ingress: set 'unlocked' flag for Qdisc ops

[Vlad Buslov]

On Wed 12 Jun 2019 at 19:33, Daniel Borkmann <daniel@iogearbox.net> wrote:
> On 06/12/2019 09:14 AM, Vlad Buslov wrote:
>> To remove rtnl lock dependency in tc filter update API when using ingress
>> Qdisc, set QDISC_CLASS_OPS_DOIT_UNLOCKED flag in ingress Qdisc_class_ops.
>>
>> Ingress Qdisc ops don't require any modifications to be used without rtnl
>> lock on tc filter update path. Ingress implementation never changes its
>> q->block and only releases it when Qdisc is being destroyed. This means it
>> is enough for RTM_{NEWTFILTER|DELTFILTER|GETTFILTER} message handlers to
>> hold ingress Qdisc reference while using it without relying on rtnl lock
>> protection. Unlocked Qdisc ops support is already implemented in filter
>> update path by unlocked cls API patch set.
>>
>> Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
>> ---
>>  net/sched/sch_ingress.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
>> index 0f65f617756b..d5382554e281 100644
>> --- a/net/sched/sch_ingress.c
>> +++ b/net/sched/sch_ingress.c
>> @@ -114,6 +114,7 @@ static int ingress_dump(struct Qdisc *sch, struct sk_buff *skb)
>>  }
>>
>>  static const struct Qdisc_class_ops ingress_class_ops = {
>> +	.flags		=	QDISC_CLASS_OPS_DOIT_UNLOCKED,
>>  	.leaf		=	ingress_leaf,
>>  	.find		=	ingress_find,
>>  	.walk		=	ingress_walk,
>>
>
> Vlad, why is clsact_class_ops not updated here? Please elaborate!

Daniel, no particular reason to not enable unlocked execution for
clsact. I set the unlocked flag for ingress because that was the Qdisc
that I tested all my parallel tc changes on. However, ingress and clsact
implementations are quite similar, so I can send a followup patch that
updates clsact_class_ops, if you want.

Re: [PATCH net-next] net: sched: ingress: set 'unlocked' flag for Qdisc ops

[Daniel Borkmann]

On 06/13/2019 09:06 AM, Vlad Buslov wrote:
> On Wed 12 Jun 2019 at 19:33, Daniel Borkmann <daniel@iogearbox.net> wrote:
>> On 06/12/2019 09:14 AM, Vlad Buslov wrote:
>>> To remove rtnl lock dependency in tc filter update API when using ingress
>>> Qdisc, set QDISC_CLASS_OPS_DOIT_UNLOCKED flag in ingress Qdisc_class_ops.
>>>
>>> Ingress Qdisc ops don't require any modifications to be used without rtnl
>>> lock on tc filter update path. Ingress implementation never changes its
>>> q->block and only releases it when Qdisc is being destroyed. This means it
>>> is enough for RTM_{NEWTFILTER|DELTFILTER|GETTFILTER} message handlers to
>>> hold ingress Qdisc reference while using it without relying on rtnl lock
>>> protection. Unlocked Qdisc ops support is already implemented in filter
>>> update path by unlocked cls API patch set.
>>>
>>> Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
>>> ---
>>>  net/sched/sch_ingress.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
>>> index 0f65f617756b..d5382554e281 100644
>>> --- a/net/sched/sch_ingress.c
>>> +++ b/net/sched/sch_ingress.c
>>> @@ -114,6 +114,7 @@ static int ingress_dump(struct Qdisc *sch, struct sk_buff *skb)
>>>  }
>>>
>>>  static const struct Qdisc_class_ops ingress_class_ops = {
>>> +	.flags		=	QDISC_CLASS_OPS_DOIT_UNLOCKED,
>>>  	.leaf		=	ingress_leaf,
>>>  	.find		=	ingress_find,
>>>  	.walk		=	ingress_walk,
>>>
>>
>> Vlad, why is clsact_class_ops not updated here? Please elaborate!
> 
> Daniel, no particular reason to not enable unlocked execution for
> clsact. I set the unlocked flag for ingress because that was the Qdisc
> that I tested all my parallel tc changes on. However, ingress and clsact
> implementations are quite similar, so I can send a followup patch that
> updates clsact_class_ops, if you want.

Yes, please do, they are pretty much the same except that clsact supersedes
ingress in that it also offers an egress hook.