netdev - Re: [PATCH net v3 2/4] flow_offload: fix incorrect cb_priv check for flow_block

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Date:   Wed, 17 Jun 2020 11:36:19 +0800
From:   wenxu <wenxu@...oud.cn>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        Simon Horman <simon.horman@...ronome.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, vladbu@...lanox.com
Subject: Re: [PATCH net v3 2/4] flow_offload: fix incorrect cb_priv check for
 flow_block_cb


On 6/17/2020 4:38 AM, Pablo Neira Ayuso wrote:
> On Tue, Jun 16, 2020 at 05:47:17PM +0200, Simon Horman wrote:
>> On Tue, Jun 16, 2020 at 11:18:16PM +0800, wenxu wrote:
>>> 在 2020/6/16 22:34, Simon Horman 写道:
>>>> On Tue, Jun 16, 2020 at 10:20:46PM +0800, wenxu wrote:
>>>>> 在 2020/6/16 18:51, Simon Horman 写道:
>>>>>> On Tue, Jun 16, 2020 at 11:19:38AM +0800, wenxu@...oud.cn wrote:
>>>>>>> From: wenxu <wenxu@...oud.cn>
>>>>>>>
>>>>>>> In the function __flow_block_indr_cleanup, The match stataments
>>>>>>> this->cb_priv == cb_priv is always false, the flow_block_cb->cb_priv
>>>>>>> is totally different data with the flow_indr_dev->cb_priv.
>>>>>>>
>>>>>>> Store the representor cb_priv to the flow_block_cb->indr.cb_priv in
>>>>>>> the driver.
>>>>>>>
>>>>>>> Fixes: 1fac52da5942 ("net: flow_offload: consolidate indirect flow_block infrastructure")
>>>>>>> Signed-off-by: wenxu <wenxu@...oud.cn>
>>>>>> Hi Wenxu,
>>>>>>
>>>>>> I wonder if this can be resolved by using the cb_ident field of struct
>>>>>> flow_block_cb.
>>>>>>
>>>>>> I observe that mlx5e_rep_indr_setup_block() seems to be the only call-site
>>>>>> where the value of the cb_ident parameter of flow_block_cb_alloc() is
>>>>>> per-block rather than per-device. So part of my proposal is to change
>>>>>> that.
>>>>> I check all the xxdriver_indr_setup_block. It seems all the cb_ident parameter of
>>>>>
>>>>> flow_block_cb_alloc is per-block. Both in the nfp_flower_setup_indr_tc_block
>>>>>
>>>>> and bnxt_tc_setup_indr_block.
>>>>>
>>>>>
>>>>> nfp_flower_setup_indr_tc_block:
>>>>>
>>>>> struct nfp_flower_indr_block_cb_priv *cb_priv;
>>>>>
>>>>> block_cb = flow_block_cb_alloc(nfp_flower_setup_indr_block_cb,
>>>>>                                                cb_priv, cb_priv,
>>>>>                                                nfp_flower_setup_indr_tc_release);
>>>>>
>>>>>
>>>>> bnxt_tc_setup_indr_block:
>>>>>
>>>>> struct bnxt_flower_indr_block_cb_priv *cb_priv;
>>>>>
>>>>> block_cb = flow_block_cb_alloc(bnxt_tc_setup_indr_block_cb,
>>>>>                                                cb_priv, cb_priv,
>>>>>                                                bnxt_tc_setup_indr_rel);
>>>>>
>>>>>
>>>>> And the function flow_block_cb_is_busy called in most place. Pass the
>>>>>
>>>>> parameter as cb_priv but not cb_indent .
>>>> Thanks, I see that now. But I still think it would be useful to understand
>>>> the purpose of cb_ident. It feels like it would lead to a clean solution
>>>> to the problem you have highlighted.
>>> I think The cb_ident means identify.  It is used to identify the each flow block cb.
>>>
>>> In the both flow_block_cb_is_busy and flow_block_cb_lookup function check
>>>
>>> the block_cb->cb_ident == cb_ident.
>> Thanks, I think that I now see what you mean about the different scope of
>> cb_ident and your proposal to allow cleanup by flow_indr_dev_unregister().
>>
>> I do, however, still wonder if there is a nicer way than reaching into
>> the structure and manually setting block_cb->indr.cb_priv
>> at each call-site.
>>
>> Perhaps a variant of flow_block_cb_alloc() for indirect blocks
>> would be nicer?
> A follow up patch to add this new variant would be good. Probably
> __flow_block_indr_binding() can go away with this new variant to set
> up the indirect flow block.


Maybe __flow_block_indr_binding() can't go away. The data and cleanup callback which should

init the flow_block_indr is only in the flow_indr_dev_setup_offload. This can't be gotten in

flow_indr_block_cb_alloc.

>