[PATCH 1/3] nvmet: make the subsystem type configurable

[Hannes Reinecke]

On 4/7/22 17:44, Christoph Hellwig wrote:
> On Thu, Apr 07, 2022 at 12:48:06PM +0200, Hannes Reinecke wrote:
>> +static ssize_t nvmet_subsys_attr_type_store(struct config_item *item,
>> +					    const char *page, size_t count)
>> +{
>> +	struct nvmet_subsys *subsys = to_subsys(item);
>> +	struct nvmet_port *p;
>> +	struct nvmet_subsys_link *s;
>> +	int i;
>> +
>> +	if (subsys->subsys_discovered)
>> +		return -EACCES;
>> +
>> +	/*
>> +	 * Do not allow to change the subsystem type if it's
>> +	 * already linked to ports; the user should unlink it first.
>> +	 */
>> +	down_read(&nvmet_config_sem);
>> +	list_for_each_entry(p, &nvmet_ports_list, global_entry) {
>> +		list_for_each_entry(s, &p->subsystems, entry) {
>> +			if (s->subsys == subsys) {
>> +				up_read(&nvmet_config_sem);
>> +				return -EACCES;
>> +			}
>> +		}
>> +	}
>> +	up_read(&nvmet_config_sem);
> 
> Does this scale?  Do we want a flag in the subsystem instead?
> 
Hmm. Seeing that it's a synchronous userspace operation I don't really 
care; worst case the 'ln -s' call takes a bit longer.
But okay, I'll have a look.

>> +	for (i = 0; i < ARRAY_SIZE(nvmet_subsys_type_map); i++) {
>> +		if (sysfs_streq(page, nvmet_subsys_type_map[i].name))
>> +			goto found;
>> +	}
>> +
>> +	pr_err("Invalid value '%s' for subsystem type\n", page);
>> +	return -EINVAL;
>> +
>> +found:
>> +	down_write(&nvmet_config_sem);
>> +	if (nvmet_subsys_type_map[i].type == NVME_NQN_CURR) {
>> +		if (!xa_empty(&subsys->namespaces)) {
>> +			pr_err("discovery subsystem cannot have namespaces\n");
>> +			return -EINVAL;
>> +		}
>> +	}
> 
> We can probably just check this unconditionally, as something that was
> a discovery subsystem before by definition can't have namespaces.

Right.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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