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[PATCH net-next v3 4/5] ip_tunnel: constify input argument of ip_tunnel_info_opts( )

Gavin Li posted 5 patches 2 years, 11 months ago
There is a newer version of this series
[PATCH net-next v3 4/5] ip_tunnel: constify input argument of ip_tunnel_info_opts( )
Posted by Gavin Li 2 years, 11 months ago 
Constify input argument(i.e. struct ip_tunnel_info *info) of
ip_tunnel_info_opts( ) so that it wouldn't be needed to W/A it each time
in each driver.

Signed-off-by: Gavin Li <gavinl@nvidia.com>
---
 include/net/ip_tunnels.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index fca357679816..32c77f149c6e 100644
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -485,9 +485,9 @@ static inline void iptunnel_xmit_stats(struct net_device *dev, int pkt_len)
 	}
 }
 
-static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
+static inline void *ip_tunnel_info_opts(const struct ip_tunnel_info *info)
 {
-	return info + 1;
+	return (void *)(info + 1);
 }
 
 static inline void ip_tunnel_info_opts_get(void *to,
-- 
2.31.1
Re: [PATCH net-next v3 4/5] ip_tunnel: constify input argument of ip_tunnel_info_opts( )
Posted by Simon Horman 2 years, 11 months ago 
On Fri, Feb 17, 2023 at 05:39:24AM +0200, Gavin Li wrote:
> Constify input argument(i.e. struct ip_tunnel_info *info) of
> ip_tunnel_info_opts( ) so that it wouldn't be needed to W/A it each time
> in each driver.
> 
> Signed-off-by: Gavin Li <gavinl@nvidia.com>
> ---
>  include/net/ip_tunnels.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
> index fca357679816..32c77f149c6e 100644
> --- a/include/net/ip_tunnels.h
> +++ b/include/net/ip_tunnels.h
> @@ -485,9 +485,9 @@ static inline void iptunnel_xmit_stats(struct net_device *dev, int pkt_len)
>  	}
>  }
>  
> -static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
> +static inline void *ip_tunnel_info_opts(const struct ip_tunnel_info *info)
>  {
> -	return info + 1;
> +	return (void *)(info + 1);

I'm unclear on what problem this is trying to solve,
but info being const, and then returning (info +1)
as non-const feels like it is masking rather than fixing a problem.

>  }
>  
>  static inline void ip_tunnel_info_opts_get(void *to,
> -- 
> 2.31.1
>
Re: [PATCH net-next v3 4/5] ip_tunnel: constify input argument of ip_tunnel_info_opts( )
Posted by Simon Horman 2 years, 11 months ago 
On Sun, Feb 19, 2023 at 09:29:21PM +0100, Simon Horman wrote:
> On Fri, Feb 17, 2023 at 05:39:24AM +0200, Gavin Li wrote:
> > Constify input argument(i.e. struct ip_tunnel_info *info) of
> > ip_tunnel_info_opts( ) so that it wouldn't be needed to W/A it each time
> > in each driver.
> > 
> > Signed-off-by: Gavin Li <gavinl@nvidia.com>
> > ---
> >  include/net/ip_tunnels.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
> > index fca357679816..32c77f149c6e 100644
> > --- a/include/net/ip_tunnels.h
> > +++ b/include/net/ip_tunnels.h
> > @@ -485,9 +485,9 @@ static inline void iptunnel_xmit_stats(struct net_device *dev, int pkt_len)
> >  	}
> >  }
> >  
> > -static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
> > +static inline void *ip_tunnel_info_opts(const struct ip_tunnel_info *info)
> >  {
> > -	return info + 1;
> > +	return (void *)(info + 1);
> 
> I'm unclear on what problem this is trying to solve,
> but info being const, and then returning (info +1)
> as non-const feels like it is masking rather than fixing a problem.

I now see that an example of the problem is added by path 5/5.

...
  CC [M]  drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.o
drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c: In function 'mlx5e_gen_ip_tunnel_header_vxlan':
drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:103:43: error: passing argument 1 of 'ip_tunnel_info_opts' discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
  103 |                 md = ip_tunnel_info_opts(e->tun_info);
      |                                          ~^~~~~~~~~~
In file included from drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:4:
./include/net/ip_tunnels.h:488:64: note: expected 'struct ip_tunnel_info *' but argument is of type 'const struct ip_tunnel_info *'
  488 | static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
      |                                         ~~~~~~~~~~~~~~~~~~~~~~~^~~~
...

But I really do wonder if this patch masks rather than fixes the problem.

> 
> >  }
> >  
> >  static inline void ip_tunnel_info_opts_get(void *to,
> > -- 
> > 2.31.1
> >
Re: [PATCH net-next v3 4/5] ip_tunnel: constify input argument of ip_tunnel_info_opts( )
Posted by Gavin Li 2 years, 11 months ago 
On 2/20/2023 4:46 AM, Simon Horman wrote:
> External email: Use caution opening links or attachments
>
>
> On Sun, Feb 19, 2023 at 09:29:21PM +0100, Simon Horman wrote:
>> On Fri, Feb 17, 2023 at 05:39:24AM +0200, Gavin Li wrote:
>>> Constify input argument(i.e. struct ip_tunnel_info *info) of
>>> ip_tunnel_info_opts( ) so that it wouldn't be needed to W/A it each time
>>> in each driver.
>>>
>>> Signed-off-by: Gavin Li <gavinl@nvidia.com>
>>> ---
>>>   include/net/ip_tunnels.h | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
>>> index fca357679816..32c77f149c6e 100644
>>> --- a/include/net/ip_tunnels.h
>>> +++ b/include/net/ip_tunnels.h
>>> @@ -485,9 +485,9 @@ static inline void iptunnel_xmit_stats(struct net_device *dev, int pkt_len)
>>>      }
>>>   }
>>>
>>> -static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
>>> +static inline void *ip_tunnel_info_opts(const struct ip_tunnel_info *info)
>>>   {
>>> -   return info + 1;
>>> +   return (void *)(info + 1);
>> I'm unclear on what problem this is trying to solve,
>> but info being const, and then returning (info +1)
>> as non-const feels like it is masking rather than fixing a problem.
> I now see that an example of the problem is added by path 5/5.
>
> ...
>    CC [M]  drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.o
> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c: In function 'mlx5e_gen_ip_tunnel_header_vxlan':
> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:103:43: error: passing argument 1 of 'ip_tunnel_info_opts' discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
>    103 |                 md = ip_tunnel_info_opts(e->tun_info);
>        |                                          ~^~~~~~~~~~
> In file included from drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:4:
> ./include/net/ip_tunnels.h:488:64: note: expected 'struct ip_tunnel_info *' but argument is of type 'const struct ip_tunnel_info *'
>    488 | static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
>        |                                         ~~~~~~~~~~~~~~~~~~~~~~~^~~~
> ...
>
> But I really do wonder if this patch masks rather than fixes the problem.
ACK
>
>>>   }
>>>
>>>   static inline void ip_tunnel_info_opts_get(void *to,
>>> --
>>> 2.31.1
>>>
Re: [PATCH net-next v3 4/5] ip_tunnel: constify input argument of ip_tunnel_info_opts( )
Posted by Gavin Li 2 years, 11 months ago 
On 2/20/2023 4:46 AM, Simon Horman wrote:
> External email: Use caution opening links or attachments
>
>
> On Sun, Feb 19, 2023 at 09:29:21PM +0100, Simon Horman wrote:
>> On Fri, Feb 17, 2023 at 05:39:24AM +0200, Gavin Li wrote:
>>> Constify input argument(i.e. struct ip_tunnel_info *info) of
>>> ip_tunnel_info_opts( ) so that it wouldn't be needed to W/A it each time
>>> in each driver.
>>>
>>> Signed-off-by: Gavin Li <gavinl@nvidia.com>
>>> ---
>>>   include/net/ip_tunnels.h | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
>>> index fca357679816..32c77f149c6e 100644
>>> --- a/include/net/ip_tunnels.h
>>> +++ b/include/net/ip_tunnels.h
>>> @@ -485,9 +485,9 @@ static inline void iptunnel_xmit_stats(struct net_device *dev, int pkt_len)
>>>      }
>>>   }
>>>
>>> -static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
>>> +static inline void *ip_tunnel_info_opts(const struct ip_tunnel_info *info)
>>>   {
>>> -   return info + 1;
>>> +   return (void *)(info + 1);
>> I'm unclear on what problem this is trying to solve,
>> but info being const, and then returning (info +1)
>> as non-const feels like it is masking rather than fixing a problem.
> I now see that an example of the problem is added by path 5/5.
>
> ...
>    CC [M]  drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.o
> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c: In function 'mlx5e_gen_ip_tunnel_header_vxlan':
> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:103:43: error: passing argument 1 of 'ip_tunnel_info_opts' discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
>    103 |                 md = ip_tunnel_info_opts(e->tun_info);
>        |                                          ~^~~~~~~~~~
> In file included from drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:4:
> ./include/net/ip_tunnels.h:488:64: note: expected 'struct ip_tunnel_info *' but argument is of type 'const struct ip_tunnel_info *'
>    488 | static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
>        |                                         ~~~~~~~~~~~~~~~~~~~~~~~^~~~
> ...
>
> But I really do wonder if this patch masks rather than fixes the problem.
Hi Olek, any comment?
>
>>>   }
>>>
>>>   static inline void ip_tunnel_info_opts_get(void *to,
>>> --
>>> 2.31.1
>>>
Re: [PATCH net-next v3 4/5] ip_tunnel: constify input argument of ip_tunnel_info_opts( )
Posted by Alexander Lobakin 2 years, 11 months ago 
From: Gavin Li <gavinl@nvidia.com>
Date: Mon, 20 Feb 2023 18:42:14 +0800

> 
> On 2/20/2023 4:46 AM, Simon Horman wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> On Sun, Feb 19, 2023 at 09:29:21PM +0100, Simon Horman wrote:
>>> On Fri, Feb 17, 2023 at 05:39:24AM +0200, Gavin Li wrote:
>>>> Constify input argument(i.e. struct ip_tunnel_info *info) of
>>>> ip_tunnel_info_opts( ) so that it wouldn't be needed to W/A it each
>>>> time
>>>> in each driver.
>>>>
>>>> Signed-off-by: Gavin Li <gavinl@nvidia.com>
>>>> ---
>>>>   include/net/ip_tunnels.h | 4 ++--
>>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
>>>> index fca357679816..32c77f149c6e 100644
>>>> --- a/include/net/ip_tunnels.h
>>>> +++ b/include/net/ip_tunnels.h
>>>> @@ -485,9 +485,9 @@ static inline void iptunnel_xmit_stats(struct
>>>> net_device *dev, int pkt_len)
>>>>      }
>>>>   }
>>>>
>>>> -static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info)
>>>> +static inline void *ip_tunnel_info_opts(const struct ip_tunnel_info
>>>> *info)
>>>>   {
>>>> -   return info + 1;
>>>> +   return (void *)(info + 1);
>>> I'm unclear on what problem this is trying to solve,
>>> but info being const, and then returning (info +1)
>>> as non-const feels like it is masking rather than fixing a problem.
>> I now see that an example of the problem is added by path 5/5.
>>
>> ...
>>    CC [M]  drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.o
>> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c: In function
>> 'mlx5e_gen_ip_tunnel_header_vxlan':
>> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:103:43:
>> error: passing argument 1 of 'ip_tunnel_info_opts' discards 'const'
>> qualifier from pointer target type [-Werror=discarded-qualifiers]
>>    103 |                 md = ip_tunnel_info_opts(e->tun_info);
>>        |                                          ~^~~~~~~~~~
>> In file included from
>> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:4:
>> ./include/net/ip_tunnels.h:488:64: note: expected 'struct
>> ip_tunnel_info *' but argument is of type 'const struct ip_tunnel_info *'
>>    488 | static inline void *ip_tunnel_info_opts(struct ip_tunnel_info
>> *info)
>>        |                                        
>> ~~~~~~~~~~~~~~~~~~~~~~~^~~~
>> ...
>>
>> But I really do wonder if this patch masks rather than fixes the problem.
> Hi Olek, any comment?

Hi,

Sorry for the late reply, was busy at work ._.

I initially proposed a solution via _Generic or __builtin_choose_expr to
return const or non-const opts basing on the input pointer type. I don't
like simple cast-aways.

See container_of_const() how it dynamically chooses whether to add
`const` or not when returning the result.

>>
>>>>   }
>>>>
>>>>   static inline void ip_tunnel_info_opts_get(void *to,
>>>> -- 
>>>> 2.31.1
>>>>

Thanks,
Olek

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