netdev - Re: [PATCH net-next v3 05/15] net: bridge: mcast: factor out port group del

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Date:   Mon, 7 Sep 2020 00:31:35 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, roopa@...dia.com,
        bridge@...ts.linux-foundation.org, davem@...emloft.net
Subject: Re: [PATCH net-next v3 05/15] net: bridge: mcast: factor out port
 group del

On 9/7/20 12:29 AM, Nikolay Aleksandrov wrote:
> On 9/6/20 11:56 PM, Jakub Kicinski wrote:
>> On Sat,  5 Sep 2020 11:24:00 +0300 Nikolay Aleksandrov wrote:
>>> @@ -843,24 +843,11 @@ static int __br_mdb_del(struct net_bridge *br, struct br_mdb_entry *entry)
>>>           if (!p->port || p->port->dev->ifindex != entry->ifindex)
>>>               continue;
>>> -        if (!hlist_empty(&p->src_list)) {
>>> -            err = -EINVAL;
>>> -            goto unlock;
>>> -        }
>>> -
>>>           if (p->port->state == BR_STATE_DISABLED)
>>>               goto unlock;
>>> -        __mdb_entry_fill_flags(entry, p->flags);
>>
>> Just from staring at the code it's unclear why the list_empty() check
>> and this __mdb_entry_fill_flags() are removed as well.
>>
> 
> The hlist_empty check is added by patch 01 temporarily for correctness.
> Otherwise I'd have to edit all open-coded pg del places and add src delete
> code and then remove it here.
> 

Obviously if I do a v4, I'll just move this patch before adding the hlist_empty
in the first place. :-)

> __mdb_entry_fill_flags() are called by __mdb_fill_info() which is the only
> function used to fill an mdb both for dumping and notifications after patch 08.
> 
>>> -        rcu_assign_pointer(*pp, p->next);
>>> -        hlist_del_init(&p->mglist);
>>> -        del_timer(&p->timer);
>>> -        kfree_rcu(p, rcu);
>>> +        br_multicast_del_pg(mp, p, pp);
>>>           err = 0;
>>> -
>>> -        if (!mp->ports && !mp->host_joined &&
>>> -            netif_running(br->dev))
>>> -            mod_timer(&mp->timer, jiffies);
>>>           break;
>>
>>
>>> +void br_multicast_del_pg(struct net_bridge_mdb_entry *mp,
>>> +             struct net_bridge_port_group *pg,
>>> +             struct net_bridge_port_group __rcu **pp)
>>> +{
>>> +    struct net_bridge *br = pg->port->br;
>>> +    struct net_bridge_group_src *ent;
>>> +    struct hlist_node *tmp;
>>> +
>>> +    rcu_assign_pointer(*pp, pg->next);
>>> +    hlist_del_init(&pg->mglist);
>>> +    del_timer(&pg->timer);
>>> +    hlist_for_each_entry_safe(ent, tmp, &pg->src_list, node)
>>> +        br_multicast_del_group_src(ent);
>>> +    br_mdb_notify(br->dev, pg->port, &pg->addr, RTM_DELMDB, pg->flags);
>>> +    kfree_rcu(pg, rcu);
>>> +
>>> +    if (!mp->ports && !mp->host_joined && netif_running(br->dev))
>>> +        mod_timer(&mp->timer, jiffies);
>>> +}
>>
>>> @@ -1641,16 +1647,7 @@ br_multicast_leave_group(struct net_bridge *br,
>>>               if (p->flags & MDB_PG_FLAGS_PERMANENT)
>>>                   break;
>>> -            rcu_assign_pointer(*pp, p->next);
>>> -            hlist_del_init(&p->mglist);
>>> -            del_timer(&p->timer);
>>> -            kfree_rcu(p, rcu);
>>> -            br_mdb_notify(br->dev, port, group, RTM_DELMDB,
>>> -                      p->flags | MDB_PG_FLAGS_FAST_LEAVE);
>>
>> And here we'll loose MDB_PG_FLAGS_FAST_LEAVE potentially?
>>
> 
> Good catch, we will lose the fast leave indeed.
> This is a 1 line change to set the flag before notifying. Would you prefer
> me to send a v4 or a follow up for it?
> 
> Thanks,
>   Nik
> 
>>> -            if (!mp->ports && !mp->host_joined &&
>>> -                netif_running(br->dev))
>>> -                mod_timer(&mp->timer, jiffies);
>>> +            br_multicast_del_pg(mp, p, pp);
>