netdev - Re: [net-next v2 3/4] openvswitch: Add meter infrastructure

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Date:   Fri, 3 Nov 2017 09:22:48 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Andy Zhou <azhou@....org>
Cc:     Greg Rose <gvrose8192@...il.com>, Joe Stringer <joe@....org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [net-next v2 3/4] openvswitch: Add meter infrastructure

On Thu, Nov 2, 2017 at 7:43 PM, Andy Zhou <azhou@....org> wrote:
> On Thu, Nov 2, 2017 at 5:07 AM, Pravin Shelar <pshelar@....org> wrote:
>> On Thu, Nov 2, 2017 at 3:07 AM, Andy Zhou <azhou@....org> wrote:
>>> On Fri, Oct 20, 2017 at 8:32 PM, Pravin Shelar <pshelar@....org> wrote:
>>>> On Thu, Oct 19, 2017 at 5:58 PM, Andy Zhou <azhou@....org> wrote:
>>>>>
>>>>> On Thu, Oct 19, 2017 at 02:47 Pravin Shelar <pshelar@....org> wrote:
>>>>>>
>>>>>> On Tue, Oct 17, 2017 at 12:36 AM, Andy Zhou <azhou@....org> wrote:
>>>>>> > OVS kernel datapath so far does not support Openflow meter action.
>>>>>> > This is the first stab at adding kernel datapath meter support.
>>>>>> > This implementation supports only drop band type.
>>>>>> >
>>>>>> > Signed-off-by: Andy Zhou <azhou@....org>
>>>>>> > ---
>>>>>> >  net/openvswitch/Makefile   |   1 +
>>>>>> >  net/openvswitch/datapath.c |  14 +-
>>>>>> >  net/openvswitch/datapath.h |   3 +
>>>>>> >  net/openvswitch/meter.c    | 604
>>>>>> > +++++++++++++++++++++++++++++++++++++++++++++
>>>>>> >  net/openvswitch/meter.h    |  54 ++++
>>>>>> >  5 files changed, 674 insertions(+), 2 deletions(-)
>>>>>> >  create mode 100644 net/openvswitch/meter.c
>>>>>> >  create mode 100644 net/openvswitch/meter.h
>>>>>> >
>>>>>> This patch mostly looks good. I have one comment below.
>>>>>>
>>>>>> > +static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info
>>>>>> > *info)
>>>>>> > +{
>>>>>> > +       struct nlattr **a = info->attrs;
>>>>>> > +       struct dp_meter *meter, *old_meter;
>>>>>> > +       struct sk_buff *reply;
>>>>>> > +       struct ovs_header *ovs_reply_header;
>>>>>> > +       struct ovs_header *ovs_header = info->userhdr;
>>>>>> > +       struct datapath *dp;
>>>>>> > +       int err;
>>>>>> > +       u32 meter_id;
>>>>>> > +       bool failed;
>>>>>> > +
>>>>>> > +       meter = dp_meter_create(a);
>>>>>> > +       if (IS_ERR_OR_NULL(meter))
>>>>>> > +               return PTR_ERR(meter);
>>>>>> > +
>>>>>> > +       reply = ovs_meter_cmd_reply_start(info, OVS_METER_CMD_SET,
>>>>>> > +                                         &ovs_reply_header);
>>>>>> > +       if (IS_ERR(reply)) {
>>>>>> > +               err = PTR_ERR(reply);
>>>>>> > +               goto exit_free_meter;
>>>>>> > +       }
>>>>>> > +
>>>>>> > +       ovs_lock();
>>>>>> > +       dp = get_dp(sock_net(skb->sk), ovs_header->dp_ifindex);
>>>>>> > +       if (!dp) {
>>>>>> > +               err = -ENODEV;
>>>>>> > +               goto exit_unlock;
>>>>>> > +       }
>>>>>> > +
>>>>>> > +       if (!a[OVS_METER_ATTR_ID]) {
>>>>>> > +               err = -ENODEV;
>>>>>> > +               goto exit_unlock;
>>>>>> > +       }
>>>>>> > +
>>>>>> > +       meter_id = nla_get_u32(a[OVS_METER_ATTR_ID]);
>>>>>> > +
>>>>>> > +       /* Cannot fail after this. */
>>>>>> > +       old_meter = lookup_meter(dp, meter_id);
>>>>>> I do not see RCU read lock taken here. This is not correctness issue
>>>>>> but it could cause RCU checker to spit out warning message. You could
>>>>>> do same trick that is done in get_dp() to avoid this issue.
>>>>>
>>>>> O.K.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Can you also test the code with rcu sparse check config option enabled?
>>>>>
>>>>>
>>>>> Do you mean to sparse compile with CONFIG_PROVE_LOCKING and
>>>>> CONFIG_DENUG_OBJECTS_RCU_HEAD?
>>>>
>>>> You could use all following options simultaneously:
>>>> CONFIG_PREEMPT
>>>> CONFIG_DEBUG_PREEMPT
>>>> CONFIG_DEBUG_SPINLOCK
>>>> CONFIG_DEBUG_ATOMIC_SLEEP
>>>> CONFIG_PROVE_RCU
>>>> CONFIG_DEBUG_OBJECTS_RCU_HEAD
>>>
>>> Thanks, I turned on those flags but did not get any error message. Do you
>>> mind share the RCU checker message?
>>
>> There would be assert failure and stack trace. so it would be pretty
>> obvious in kernel log messages.
>> Let me know if you do not see any stack trace while running meter
>> create, delete and execute.
>
> No I did not see them.
ok, Can you send out patch against latest net-next?