[Question] nvme namespace enumerated to 2 when hot-reinserted into a server in 5.14 kernel(RHEL 9.1)

[Munoz Ruiz, Francisco]

Hi,


We are hardening our tests for RHEL, and we'd like to know if this is 
the expected behavior.

After a couple of tests via trace-cmd and booting with 
nvme_core.multipath=N, we found that the number "2" presented to 
userspace comes from nvme_init_ns_head()->nvme_alloc_ns_head() when an 
SSD is hot-reinserted


ret = ida_simple_get(&ctrl->subsys->ns_ida, 1, 0, GFP_KERNEL);
if (ret < 0)
	goto out_free_head;
head->instance = ret;

Then in nvme_alloc_ns() the string representing a disk name is assembled 
via sprintf because nvme_mpath_set_disk_name returns immediately due to 
multipath == false
/*
  * Without the multipath code enabled, multiple controller per
  * subsystems are visible as devices and thus we cannot use the
  * subsystem instance.
  */
if (!nvme_mpath_set_disk_name(ns, disk->disk_name, &disk->flags))
	sprintf(disk->disk_name, "nvme%dn%d", ctrl->instance,
		ns->head->instance);
ns->disk = disk;


We also observed that the ida API used in core.c was updated in a recent 
commit 8b850475c08caa9545c460d7. Does this fix the namespace numbering 
presented to the user via disk_name? if not, should we pass our tests if 
nvmeXn2 is observed instead of nvmeXn1 when hot-reinserting an SSD?

Thanks,
Francisco.