Re: [PATCH net-next v8 2/5] net: add a generation counter for dev->mc changes

[Nicolas Dichtel <nicolas.dichtel@6wind.com>]

Le 28/09/2026 à 09:53, Nicolas Dichtel a écrit :
> 
> 
> Le 27/09/2026 à 02:24, Yuyang Huang a écrit :
>> A multi-part RTM_GETMULTICAST dump of dev->mc resumes by position, so
>> entries added or removed between two dump rounds can be skipped or
>> repeated. The IPv4 and IPv6 dumps report that with NLM_F_DUMP_INTR by
>> stamping cb->seq from a per netns generation counter combined with
>> dev_base_seq, see inet_base_seq().
>>
>> Add the equivalent for the device multicast lists: a per netns counter
>> bumped whenever an entry is added to or removed from any dev->mc. The
>> list helpers do not know which device a list belongs to, so give
>> netdev_hw_addr_list an owner, set for the lists of a device and NULL
>> for snapshots and other standalone lists, and change list->count
>> through helpers that bump the counter of dev_net(owner) when the list
>> is dev->mc. That covers the dev_mc_* helpers, both lists of a sync,
>> the hardware sync helpers drivers call from their rx mode callbacks or
>> their own workers and the reconciliation after an asynchronous rx mode
>> update. It is atomic since the writers only hold the address lock of
>> their own device.
>>
>> Used by the following patch for the AF_PACKET multicast dump.
>>
>> Signed-off-by: Yuyang Huang <sigefriedhyy@gmail.com>
> 
> 
> If another version is needed, you can rename counter to _counter to highlight
> that the helpers should be used.
Sorry, this sentence is a leftover from the first version of my reply.

[snip]

> 
> For correctness, __hw_addr_splice() should use helper:
> 
> @@ -509,8 +509,8 @@ static void __hw_addr_splice(struct netdev_hw_addr_list *dst,
>  {
>          src->tree = RB_ROOT;
>          list_splice_init(&src->list, &dst->list);
> -        dst->count += src->count;
> -        src->count = 0;
> +        __hw_addr_count_add(dst, src->count);
> +        __hw_addr_count_reset(src);
>  }
> 
> Renaming  struct netdev_hw_addr_list->count to _count would help to check all
> users and highlight that modifying _count should be done with helpers.

This comment stands.

Regards,
Nicolas