[PATCH] nvmet: implement unique discovery NQN

[Sagi Grimberg]

So it also responds for the default discovery-nqn?

On 12/11/23 10:10, hare at kernel.org wrote:
> From: Hannes Reinecke <hare at suse.de>
> 
> Add a configfs attribute 'discovery_nqn' in the 'nvmet' configfs
> directory to specify the unique discovery NQN.
> 
> Signed-off-by: Hannes Reinecke <hare at suse.de>
> ---
>   drivers/nvme/target/configfs.c | 45 ++++++++++++++++++++++++++++++++++
>   drivers/nvme/target/core.c     |  7 ++++++
>   2 files changed, 52 insertions(+)
> 
> diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
> index d937fe05129e..88911d0cd057 100644
> --- a/drivers/nvme/target/configfs.c
> +++ b/drivers/nvme/target/configfs.c
> @@ -1587,6 +1587,11 @@ static struct config_group *nvmet_subsys_make(struct config_group *group,
>   		return ERR_PTR(-EINVAL);
>   	}
>   
> +	if (sysfs_streq(name, nvmet_disc_subsys->subsysnqn)) {
> +		pr_err("can't create subsystem using unique discovery NQN\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
>   	subsys = nvmet_subsys_alloc(name, NVME_NQN_NVME);
>   	if (IS_ERR(subsys))
>   		return ERR_CAST(subsys);
> @@ -2131,7 +2136,47 @@ static const struct config_item_type nvmet_hosts_type = {
>   
>   static struct config_group nvmet_hosts_group;
>   
> +static ssize_t nvmet_root_discovery_nqn_show(struct config_item *item,
> +					     char *page)
> +{
> +	return sprintf(page, "%s\n", nvmet_disc_subsys->subsysnqn);
> +}
> +
> +static ssize_t nvmet_root_discovery_nqn_store(struct config_item *item,
> +		const char *page, size_t count)
> +{
> +	size_t len;
> +	struct list_head *entry;
> +
> +	len = strcspn(page, "\n");
> +	if (!len || len > NVMF_NQN_FIELD_LEN - 1)
> +		return -EINVAL;
> +
> +	down_write(&nvmet_config_sem);
> +	list_for_each(entry, &nvmet_subsystems_group.cg_children) {
> +		struct config_item *item = container_of(entry, struct config_item, ci_entry);
> +		if (!strncmp(config_item_name(item), page, len)) {
> +			pr_err("duplicate NQN %s\n", config_item_name(item));
> +			up_write(&nvmet_config_sem);
> +			return -EINVAL;
> +		}
> +	}
> +	memset(nvmet_disc_subsys->subsysnqn, 0, NVMF_NQN_FIELD_LEN);
> +	memcpy(nvmet_disc_subsys->subsysnqn, page, len);
> +	up_write(&nvmet_config_sem);
> +
> +	return len;
> +}
> +
> +CONFIGFS_ATTR(nvmet_root_, discovery_nqn);
> +
> +static struct configfs_attribute *nvmet_root_attrs[] = {
> +	&nvmet_root_attr_discovery_nqn,
> +	NULL,
> +};
> +
>   static const struct config_item_type nvmet_root_type = {
> +	.ct_attrs		= nvmet_root_attrs,
>   	.ct_owner		= THIS_MODULE,
>   };
>   
> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index 3935165048e7..9c028bbedb45 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -1530,6 +1530,13 @@ static struct nvmet_subsys *nvmet_find_get_subsys(struct nvmet_port *port,
>   	}
>   
>   	down_read(&nvmet_config_sem);
> +	if (!strncmp(nvmet_disc_subsys->subsysnqn, subsysnqn,
> +				NVMF_NQN_SIZE)) {
> +		if (kref_get_unless_zero(&nvmet_disc_subsys->ref)) {
> +			up_read(&nvmet_config_sem);
> +			return nvmet_disc_subsys;
> +		}
> +	}
>   	list_for_each_entry(p, &port->subsystems, entry) {
>   		if (!strncmp(p->subsys->subsysnqn, subsysnqn,
>   				NVMF_NQN_SIZE)) {