Re: [PATCH V3 0/3] Ensure ordered namespace registration during async scan

[Keith Busch <kbusch@kernel.org>]

On Thu, Feb 26, 2026 at 11:35:15AM -0500, John Meneghini wrote:
> It's worse than this.  Yes, in RHEL we carry out of tree patches to tun off the async scanning with SCSI,
> and we reverted this async namespace scanning patch in NVMe.
> 
> We had to do this because, as soon as we turned these async scanning mechanisms on, we immediately
> received customer escalations. Customer were not able to upgrade their systems. We have customer issues
> and complaints open about this and we see this async namespace scanning as a barrier to adoption with NVMEe -
> especially with NVME-OF which tends to have many more Namespaces than PCIe.

Sounds like some people just don't know how to use labels or persistent
names. Relying on /dev/nvmeXnY or /dev/sdX to always be a handle to the
same device is a fragile solution.
 
> And yes, the PCIe async discovery stuff does cause some problems.  The difference is: the PCIe bus configuration does
> not change nearly as often as, e.g., the nvme namespace configuration in a fabric, so customers don't notice the changing pci ids.
> Unless some one is going lots of hot unplugging and plugging with their PCI bus, the PCI ids typically don't change at all.

It's not about the PCI topology changing. The async probe makes it
non-deterministic as to which PCI device is going to claim which
instance out of the nvme ida since they all try to run concurrently.