linux-kernel - Re: [RFC PATCH net-next 4/6] net/smc: support max connections per lgr negotiation

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Message-ID: <ZMvqJ6FYR6gWS+ZK@kernel.org>
Date:   Thu, 3 Aug 2023 19:55:51 +0200
From:   Simon Horman <horms@...nel.org>
To:     Guangguan Wang <guangguan.wang@...ux.alibaba.com>
Cc:     wenjia@...ux.ibm.com, jaka@...ux.ibm.com, kgraul@...ux.ibm.com,
        tonylu@...ux.alibaba.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, alibuda@...ux.alibaba.com,
        guwen@...ux.alibaba.com, linux-s390@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net-next 4/6] net/smc: support max connections per
 lgr negotiation

On Thu, Aug 03, 2023 at 09:24:20PM +0800, Guangguan Wang wrote:
> Support max connections per lgr negotiation for SMCR v2.1,
> which is one of smc v2.1 features.
> 
> Signed-off-by: Guangguan Wang <guangguan.wang@...ux.alibaba.com>
> Reviewed-by: Tony Lu <tonylu@...ux.alibaba.com>

...

Hi Guangguan Wang,

>  int smc_clc_cli_v2x_features_validate(struct smc_clc_first_contact_ext *fce,
>  				      struct smc_init_info *ini)
>  {
> +	struct smc_clc_first_contact_ext_v2x *fce_v2x =
> +		(struct smc_clc_first_contact_ext_v2x *)fce;
> +
>  	if (ini->release_ver < SMC_RELEASE_1)
>  		return 0;
>  
> +	if (!ini->is_smcd) {
> +		if (fce_v2x->max_conns > SMC_CONN_PER_LGR_MAX)

The type of the max_cons field is u8.
The value of SMC_CONN_PER_LGR_MAX is 255 (in another patch of this series),
the maximum value that the max_cons field can be assigned.
So it seems that this condition cannot ever be true.

As flagged by Smatch.

> +			return SMC_CLC_DECL_MAXCONNERR;
> +		ini->max_conns = fce_v2x->max_conns;
> +	}
> +
>  	return 0;
>  }

...

> diff --git a/net/smc/smc_clc.h b/net/smc/smc_clc.h

...

> @@ -236,7 +238,8 @@ struct smc_clc_first_contact_ext {
>  
>  struct smc_clc_first_contact_ext_v2x {
>  	struct smc_clc_first_contact_ext fce_v20;
> -	u8 reserved3[4];
> +	u8 max_conns; /* for SMC-R only */
> +	u8 reserved3[3];
>  	__be32 vendor_exp_options;
>  	u8 reserved4[8];
>  } __packed;		/* format defined in

...

> diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
> index 1a97fef39127..065369dc6584 100644
> --- a/net/smc/smc_core.h
> +++ b/net/smc/smc_core.h
> @@ -22,6 +22,7 @@
>  #include "smc_ib.h"
>  
>  #define SMC_RMBS_PER_LGR_MAX	255	/* max. # of RMBs per link group */
> +#define SMC_CONN_PER_LGR_MAX	255	/* max. # of connections per link group */
>  
>  struct smc_lgr_list {			/* list of link group definition */
>  	struct list_head	list;