netdev - Re: [Patch net-next v2 2/2] net_sched: add network namespace support for tc actions

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Message-ID: <CAM_iQpVVe28XUkSfR1OhwMq6mgJVQ_zcPJn+xmLpb_YDy0wsDg@mail.gmail.com>
Date:	Tue, 23 Feb 2016 14:23:21 -0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Jamal Hadi Salim <jhs@...atatu.com>
Cc:	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [Patch net-next v2 2/2] net_sched: add network namespace support
 for tc actions

On Tue, Feb 23, 2016 at 5:14 AM, Jamal Hadi Salim <jhs@...atatu.com> wrote:
> On 16-02-22 06:57 PM, Cong Wang wrote:
>
> [..]
>
>>
>> diff --git a/include/net/act_api.h b/include/net/act_api.h
>> index 8c4e3ff..342be6c 100644
>> --- a/include/net/act_api.h
>> +++ b/include/net/act_api.h
>> @@ -7,6 +7,8 @@
>>
>>   #include <net/sch_generic.h>
>>   #include <net/pkt_sched.h>
>> +#include <net/net_namespace.h>
>> +#include <net/netns/generic.h>
>>
>>   struct tcf_common {
>>         struct hlist_node               tcfc_head;
>> @@ -87,31 +89,65 @@ struct tc_action {
>>         __u32                   type; /* for backward
>> compat(TCA_OLD_COMPAT) */
>>         __u32                   order;
>>         struct list_head        list;
>> +       struct tcf_hashinfo     *hinfo;
>>   };
>>
>
> It doesnt seem neccessary to have hinfo in tc_action. Quick scan:
> __tcf_hash_release() seems to be the only other place that uses it.
> And the callers to that appear capable of passing the struct
> net or tn  which eventually propagates up...

The tcf_action_destroy() callchain still can't find out hinfo yet.

I know this is one of the ugly parts, this is why I mentioned it
in the changelog that we should refactor it. Do you mind if I
refactor this later?

>
>>   struct tc_action_ops {
>>         struct list_head head;
>> -       struct tcf_hashinfo *hinfo;
>>         char    kind[IFNAMSIZ];
>>         __u32   type; /* TBD to match kind */
>>         struct module           *owner;
>>         int     (*act)(struct sk_buff *, const struct tc_action *, struct
>> tcf_result *);
>>         int     (*dump)(struct sk_buff *, struct tc_action *, int, int);
>>         void    (*cleanup)(struct tc_action *, int bind);
>> -       int     (*lookup)(struct tc_action *, u32);
>> +       int     (*lookup)(struct net *, struct tc_action *, u32);
>>         int     (*init)(struct net *net, struct nlattr *nla,
>>                         struct nlattr *est, struct tc_action *act, int
>> ovr,
>>                         int bind);
>> -       int     (*walk)(struct sk_buff *, struct netlink_callback *, int,
>> struct tc_action *);
>> +       int     (*walk)(struct net *, struct sk_buff *,
>> +                       struct netlink_callback *, int, struct tc_action
>> *);
>> +};
>> +
>
>
> Do you really need to pass struct net to walk(); is deriving from skb
> not sufficient?

Yes, seems you are right.


>
>
>> +       int err = 0;
>
>
>
>> diff --git a/net/sched/act_api.c b/net/sched/act_api.c
>> index acafaf7..9606666 100644
>> --- a/net/sched/act_api.c
>> +++ b/net/sched/act_api.c
>> @@ -36,10 +36,9 @@ static void free_tcf(struct rcu_head *head)
>>         kfree(p);
>>   }
>>
>> -static void tcf_hash_destroy(struct tc_action *a)
>> +static void tcf_hash_destroy(struct tcf_hashinfo *hinfo, struct tc_action
>> *a)
>>   {
>>         struct tcf_common *p = a->priv;
>> -       struct tcf_hashinfo *hinfo = a->ops->hinfo;
>>
>>         spin_lock_bh(&hinfo->lock);
>>         hlist_del(&p->tcfc_head);
>> @@ -68,7 +67,7 @@ int __tcf_hash_release(struct tc_action *a, bool bind,
>> bool strict)
>>                 if (p->tcfc_bindcnt <= 0 && p->tcfc_refcnt <= 0) {
>>                         if (a->ops->cleanup)
>>                                 a->ops->cleanup(a, bind);
>> -                       tcf_hash_destroy(a);
>> +                       tcf_hash_destroy(a->hinfo, a);
>
>
>
> So this seems to be the only place where a->hinfo is read from. The
> rest seems to just set a->hinfo.
> I took a quick look at __tcf_hash_release() and all calling sites
> are net/tn aware already.


tcf_action_destroy().


>
>> -u32 tcf_hash_new_index(struct tcf_hashinfo *hinfo)
>> +u32 tcf_hash_new_index(struct tc_action_net *tn)
>>   {
>> +       struct tcf_hashinfo *hinfo = tn->hinfo;
>>         u32 val = hinfo->index;
>>
>
>
> That also seemed unneeded. You could have derived hinfo
> from tn.

This is a pure taste of the API, I want to hide the hinfo as much as
I can and expose tn to callers.

>
> Otherwise looks reasonable. I was hoping we could get rid of the per
> action pernet ops but that could come later.
>

That is hard (if not impossible), because we have to allocate the pernet
ops on heap, which seems not doable.


Thanks!