Re: [PATCH net-next v4 03/18] net/smc: extract v2 check helper from SMC-D device registration

[Jan Karcher <jaka@linux.ibm.com>]

On 24/09/2023 17:16, Wen Gu wrote:
> This patch extracts v2-capable logic from the process of registering the
> ISM device as an SMC-D device, so that the registration process of other
> underlying devices can reuse it.
> 
> Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
> ---
>   net/smc/smc_ism.c | 29 ++++++++++++++++++-----------
>   net/smc/smc_ism.h |  1 +
>   2 files changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
> index 455ae0a..8f1ba74 100644
> --- a/net/smc/smc_ism.c
> +++ b/net/smc/smc_ism.c
> @@ -69,6 +69,22 @@ bool smc_ism_is_v2_capable(void)
>   	return smc_ism_v2_capable;
>   }
>   
> +/* must be called under smcd_dev_list.mutex lock */
> +void smc_ism_check_v2_capable(struct smcd_dev *smcd)
> +{
> +	u8 *system_eid = NULL;
> +
> +	if (smc_ism_v2_capable)
> +		return;
> +
> +	system_eid = smcd->ops->get_system_eid();
> +	if (smcd->ops->supports_v2()) {
> +		smc_ism_v2_capable = true;
> +		memcpy(smc_ism_v2_system_eid, system_eid,
> +		       SMC_MAX_EID_LEN);
> +	}
> +}
> +
>   /* Set a connection using this DMBE. */
>   void smc_ism_set_conn(struct smc_connection *conn)
>   {
> @@ -423,16 +439,7 @@ static void smcd_register_dev(struct ism_dev *ism)
>   		smc_pnetid_by_table_smcd(smcd);
>   
>   	mutex_lock(&smcd_dev_list.mutex);
> -	if (list_empty(&smcd_dev_list.list)) {
> -		u8 *system_eid = NULL;
> -
> -		system_eid = smcd->ops->get_system_eid();
> -		if (smcd->ops->supports_v2()) {
> -			smc_ism_v2_capable = true;
> -			memcpy(smc_ism_v2_system_eid, system_eid,
> -			       SMC_MAX_EID_LEN);
> -		}
> -	}
> +	smc_ism_check_v2_capable(smcd);

The list_empty check is omitted here which means the 
smc_ism_check_v2_capable does not touch the list.
So i think the call could be placed prior the mutex_lock.

>   	/* sort list: devices without pnetid before devices with pnetid */
>   	if (smcd->pnetid[0])
>   		list_add_tail(&smcd->list, &smcd_dev_list.list);
> @@ -535,10 +542,10 @@ int smc_ism_init(void)
>   {
>   	int rc = 0;
>   
> -#if IS_ENABLED(CONFIG_ISM)
>   	smc_ism_v2_capable = false;
>   	memset(smc_ism_v2_system_eid, 0, SMC_MAX_EID_LEN);
>   
> +#if IS_ENABLED(CONFIG_ISM)
>   	rc = ism_register_client(&smc_ism_client);
>   #endif
>   	return rc;
> diff --git a/net/smc/smc_ism.h b/net/smc/smc_ism.h
> index 832b2f4..14d2e77 100644
> --- a/net/smc/smc_ism.h
> +++ b/net/smc/smc_ism.h
> @@ -42,6 +42,7 @@ int smc_ism_register_dmb(struct smc_link_group *lgr, int buf_size,
>   void smc_ism_get_system_eid(u8 **eid);
>   u16 smc_ism_get_chid(struct smcd_dev *dev);
>   bool smc_ism_is_v2_capable(void);
> +void smc_ism_check_v2_capable(struct smcd_dev *dev);
>   int smc_ism_init(void);
>   void smc_ism_exit(void);
>   int smcd_nl_get_device(struct sk_buff *skb, struct netlink_callback *cb);