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

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Date:   Thu, 2 Nov 2017 19:43:41 -0700
From:   Andy Zhou <azhou@....org>
To:     Pravin Shelar <pshelar@....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 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.