linux-kernel - Re: [PATCH v2 17/17] ibmvfc: provide modules parameters for MQ settings

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Date:   Wed, 2 Dec 2020 12:40:44 -0600
From:   Brian King <brking@...ux.vnet.ibm.com>
To:     Tyrel Datwyler <tyreld@...ux.ibm.com>,
        james.bottomley@...senpartnership.com
Cc:     martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        brking@...ux.ibm.com
Subject: Re: [PATCH v2 17/17] ibmvfc: provide modules parameters for MQ
 settings

On 12/1/20 6:53 PM, Tyrel Datwyler wrote:
> +module_param_named(mig_channels_only, mig_channels_only, uint, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(mig_channels_only, "Prevent migration to non-channelized system. "
> +		 "[Default=" __stringify(IBMVFC_MIG_NO_SUB_TO_CRQ) "]");
> +module_param_named(mig_no_less_channels, mig_no_less_channels, uint, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(mig_no_less_channels, "Prevent migration to system with less channels. "
> +		 "[Default=" __stringify(IBMVFC_MIG_NO_N_TO_M) "]");

Both of these are writeable, but it doesn't look like you do any re-negotiation
with the VIOS for these changed settings to take effect if someone changes
them at runtime.

> +
>  module_param_named(init_timeout, init_timeout, uint, S_IRUGO | S_IWUSR);
>  MODULE_PARM_DESC(init_timeout, "Initialization timeout in seconds. "
>  		 "[Default=" __stringify(IBMVFC_INIT_TIMEOUT) "]");

> @@ -3228,6 +3250,36 @@ static ssize_t ibmvfc_store_log_level(struct device *dev,
>  	return strlen(buf);
>  }
>  
> +static ssize_t ibmvfc_show_scsi_channels(struct device *dev,
> +					 struct device_attribute *attr, char *buf)
> +{
> +	struct Scsi_Host *shost = class_to_shost(dev);
> +	struct ibmvfc_host *vhost = shost_priv(shost);
> +	unsigned long flags = 0;
> +	int len;
> +
> +	spin_lock_irqsave(shost->host_lock, flags);
> +	len = snprintf(buf, PAGE_SIZE, "%d\n", vhost->client_scsi_channels);
> +	spin_unlock_irqrestore(shost->host_lock, flags);
> +	return len;
> +}
> +
> +static ssize_t ibmvfc_store_scsi_channels(struct device *dev,
> +					 struct device_attribute *attr,
> +					 const char *buf, size_t count)
> +{
> +	struct Scsi_Host *shost = class_to_shost(dev);
> +	struct ibmvfc_host *vhost = shost_priv(shost);
> +	unsigned long flags = 0;
> +	unsigned int channels;
> +
> +	spin_lock_irqsave(shost->host_lock, flags);
> +	channels = simple_strtoul(buf, NULL, 10);
> +	vhost->client_scsi_channels = min(channels, nr_scsi_hw_queues);

Don't we need to do a LIP here for this new setting to go into effect?

> +	spin_unlock_irqrestore(shost->host_lock, flags);
> +	return strlen(buf);
> +}
> +
>  static DEVICE_ATTR(partition_name, S_IRUGO, ibmvfc_show_host_partition_name, NULL);
>  static DEVICE_ATTR(device_name, S_IRUGO, ibmvfc_show_host_device_name, NULL);
>  static DEVICE_ATTR(port_loc_code, S_IRUGO, ibmvfc_show_host_loc_code, NULL);



-- 
Brian King
Power Linux I/O
IBM Linux Technology Center