[PATCH v3 1/3] nvmet: Expose max queues to sysfs

[Hannes Reinecke]

On 8/29/22 10:38, Daniel Wagner wrote:
> Allow to set the max queues the target supports. This is useful for
> testing the reconnect attempt of the host with changing numbers of
> supported queues.
> 
> Signed-off-by: Daniel Wagner <dwagner at suse.de>
> ---
>   drivers/nvme/target/configfs.c | 28 ++++++++++++++++++++++++++++
>   1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
> index 2bcd60758919..a415c2987393 100644
> --- a/drivers/nvme/target/configfs.c
> +++ b/drivers/nvme/target/configfs.c
> @@ -1281,6 +1281,33 @@ static ssize_t nvmet_subsys_attr_pi_enable_store(struct config_item *item,
>   CONFIGFS_ATTR(nvmet_subsys_, attr_pi_enable);
>   #endif
>   
> +static ssize_t nvmet_subsys_attr_qid_max_show(struct config_item *item,
> +					      char *page)
> +{
> +	return snprintf(page, PAGE_SIZE, "%u\n", to_subsys(item)->max_qid);
> +}
> +
> +static ssize_t nvmet_subsys_attr_qid_max_store(struct config_item *item,
> +					       const char *page, size_t cnt)
> +{
> +	u16 qid_max;
> +
> +	if (nvmet_is_port_enabled(port, __func__))
> +		return -EACCES;
> +
> +	if (sscanf(page, "%hu\n", &qid_max) != 1)
> +		return -EINVAL;
> +
> +	if (qid_max < 1 || qid_max > NVMET_NR_QUEUES)
> +		return -EINVAL;
> +
> +	down_write(&nvmet_config_sem);
> +	to_subsys(item)->max_qid = qid_max;
> +	up_write(&nvmet_config_sem);
> +	return cnt;
> +}
> +CONFIGFS_ATTR(nvmet_subsys_, attr_qid_max);
> +
>   static struct configfs_attribute *nvmet_subsys_attrs[] = {
>   	&nvmet_subsys_attr_attr_allow_any_host,
>   	&nvmet_subsys_attr_attr_version,
> @@ -1291,6 +1318,7 @@ static struct configfs_attribute *nvmet_subsys_attrs[] = {
>   #ifdef CONFIG_BLK_DEV_INTEGRITY
>   	&nvmet_subsys_attr_attr_pi_enable,
>   #endif
> +	&nvmet_subsys_attr_attr_qid_max,
>   	NULL,
>   };
>   
Minor nit: I would add the new field prior to the 'ifdef' stuff; as it 
stands the layout of the resulting structure changes depending on the 
configuration, which tends to cause all sorts of issues for distributions.
But otherwise:

Reviewed-by: Hannes Reinecke <hare at suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare at suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer