linux-kernel - Re: [PATCH net-next 1/2] net: sparx5: flower: cleanup sparx5_tc_flower_handler_control

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Message-ID: <8e112b31-0168-4e82-a378-87211ea99cfa@fiberby.net>
Date: Tue, 23 Apr 2024 16:25:53 +0000
From: Asbjørn Sloth Tønnesen <ast@...erby.net>
To: Daniel Machon <daniel.machon@...rochip.com>
Cc: netdev@...r.kernel.org, Steen Hegelund <Steen.Hegelund@...rochip.com>,
 Lars Povlsen <lars.povlsen@...rochip.com>, UNGLinuxDriver@...rochip.com,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 linux-kernel@...r.kernel.org, Jacob Keller <jacob.e.keller@...el.com>
Subject: Re: [PATCH net-next 1/2] net: sparx5: flower: cleanup
 sparx5_tc_flower_handler_control_usage()

Hi Daniel,

Thank you for the review.

On 4/23/24 11:15 AM, Daniel Machon wrote:
> Hi Asbjørn,
> 
> Thank you for your patch!
> 
>> Define extack locally, to reduce line lengths and future users.
>>
>> Only perform fragment handling, when at least one fragment flag is set.
>>
>> Remove goto, as it's only used once, and the error message is specific
>> to that context.
>>
>> Only compile tested.
>>
>> Signed-off-by: Asbjørn Sloth Tønnesen <ast@...erby.net>
>> ---
>>   .../ethernet/microchip/sparx5/sparx5_tc_flower.c    | 13 ++++++-------
>>   1 file changed, 6 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_tc_flower.c b/drivers/net/ethernet/microchip/sparx5/sparx5_tc_flower.c
>> index 663571fe7b2d..d846edd77a01 100644
>> --- a/drivers/net/ethernet/microchip/sparx5/sparx5_tc_flower.c
>> +++ b/drivers/net/ethernet/microchip/sparx5/sparx5_tc_flower.c
>> @@ -159,13 +159,14 @@ sparx5_tc_flower_handler_basic_usage(struct vcap_tc_flower_parse_usage *st)
>>   static int
>>   sparx5_tc_flower_handler_control_usage(struct vcap_tc_flower_parse_usage *st)
>>   {
>> +       struct netlink_ext_ack *extack = st->fco->common.extack;
> 
> Could you please update the use of extack in all places inside this
> function. You are missing one place.

Good catch, sure. It must have got lost somewhere along the way. I deliberately kept it out
of the net patch, since it could wait for net-next.

>>          struct flow_match_control mt;
>>          u32 value, mask;
>>          int err = 0;
>>
>>          flow_rule_match_control(st->frule, &mt);
>>
>> -       if (mt.mask->flags) {
>> +       if (mt.mask->flags & (FLOW_DIS_IS_FRAGMENT | FLOW_DIS_FIRST_FRAG)) {
> 
> Since these flags are used here and in the next patch, maybe assign them
> to a variable:
> 
> u32 supp_flags = FLOW_DIS_IS_FRAGMENT | FLOW_DIS_FIRST_FRAG
> 
> And update the use throughout.

In an earlier state this patch had a #define SPARX5_FLOWER_SUPPORTED_CTLFLAGS,
in the same style as nfp in drivers/net/ethernet/netronome/nfp/flower/offload.c

Right now, this driver supports all currently defined flags (which are used with mask),
so the point of using flow_rule_is_supp_control_flags() to this dirver, is to
make it possible to introduce new flags in the future, without having to update
all drivers to explicitly not support a new flag.

My problem with using supp_flags in both places is: What happens when support
for a new flag is introduced?

u32 supp_flags = FLOW_DIS_IS_FRAGMENT | FLOW_DIS_FIRST_FRAG | FLOW_DIS_NEW_FLAG;

if (mt.mask->flags & (FLOW_DIS_IS_FRAGMENT | FLOW_DIS_FIRST_FRAG))
         /* handle fragment flags through lookup table */

if (mt.mask->flags & FLOW_DIS_NEW_FLAG)
         /* do something */

if (!flow_rule_is_supp_control_flags(supp_flags, mt.mask->flags, extack))
         return -EOPNOTSUPP;

The fragment lookup table code currently requires the above guarding,
as [0][0] in the lookup table is FRAG_INVAL, and not FRAG_SHRUG.

What do you think?

-- 
Best regards
Asbjørn Sloth Tønnesen
Network Engineer
Fiberby - AS42541