Subject: Re: [PATCH net-next 04/12] net: sched: flower: track filter deletion with flag

From: Vlad Buslov <[email-masked]>
Date: Fri, 15 Feb 2019 15:54:54 +0000

On Thu 14 Feb 2019 at 20:49, Stefano Brivio <[email-masked]> wrote:
> On Thu, 14 Feb 2019 09:47:04 +0200
> Vlad Buslov <[email-masked]> wrote:
>
>> +static int __fl_delete(struct tcf_proto *tp, struct cls_fl_filter *f,
>> +		       bool *last, struct netlink_ext_ack *extack)
>
> This would be easier to follow (at least for me):
>
>>  {
>>  	struct cls_fl_head *head = fl_head_dereference(tp);
>>  	bool async = tcf_exts_get_net(&f->exts);
>> -	bool last;
>> -
>> -	idr_remove(&head->handle_idr, f->handle);
>> -	list_del_rcu(&f->list);
>> -	last = fl_mask_put(head, f->mask, async);
>> -	if (!tc_skip_hw(f->flags))
>> -		fl_hw_destroy_filter(tp, f, extack);
>> -	tcf_unbind_filter(tp, &f->res);
>> -	__fl_put(f);
>> +	int err = 0;
>
> without this
>
>> +
>> +	(*last) = false;
>
> with *last = false;
>
>> +
>> +	if (!f->deleted) {
>
> with:
> 	if (f->deleted)
> 		return -ENOENT;
>
>> +		f->deleted = true;
>> +		rhashtable_remove_fast(&f->mask->ht, &f->ht_node,
>> +				       f->mask->filter_ht_params);
>> +		idr_remove(&head->handle_idr, f->handle);
>> +		list_del_rcu(&f->list);
>> +		(*last) = fl_mask_put(head, f->mask, async);
>
> with:
> 	*last = fl_mask_put(head, f->mask, async);
>
>> +		if (!tc_skip_hw(f->flags))
>> +			fl_hw_destroy_filter(tp, f, extack);
>> +		tcf_unbind_filter(tp, &f->res);
>> +		__fl_put(f);
>
> and a return 0; here

Agree, this function looks better when structured in the way you
suggest. Will change it in V2.

>
>> +	} else {
>> +		err = -ENOENT;
>> +	}
>>  
>> -	return last;
>> +	return err;
>>  }
>>  
>> [...]
>>
>> @@ -1520,14 +1541,14 @@ static int fl_delete(struct tcf_proto *tp, void *arg, bool *last,
>>  {
>>  	struct cls_fl_head *head = fl_head_dereference(tp);
>>  	struct cls_fl_filter *f = arg;
>> +	bool last_on_mask;
>
> This is unused in this series, maybe change __fl_delete() to optionally
> take NULL as 'bool *last' argument?

It was implemented like that originally, but on internal review with
Jiri we decided that having unused variable here is better than
complicating __fl_delete() with support for "last" being NULL without
good reason.

>
>> +	int err = 0;
>
> Nit: no need to initialise this.

Yes, but I always regret having uninitialized variables in my functions
later on :(

>  
>> -	rhashtable_remove_fast(&f->mask->ht, &f->ht_node,
>> -			       f->mask->filter_ht_params);
>> -	__fl_delete(tp, f, extack);
>> +	err = __fl_delete(tp, f, &last_on_mask, extack);
>>  	*last = list_empty(&head->masks);
>>  	__fl_put(f);
>>  
>> -	return 0;
>> +	return err;
>>  }
>>  
>>  static void fl_walk(struct tcf_proto *tp, struct tcf_walker *arg,