Re: [PATCH 0/8] dax/kmem: atomic whole-device hotplug via sysfs

[Andrew Morton]

On Sat, 21 Mar 2026 11:03:56 -0400 Gregory Price <gourry@xxxxxxxxxx> wrote:

> The dax kmem driver currently onlines memory during probe using the
> system default policy, with no way to control or query the region state
> at runtime - other than by inspecting the state of individual blocks.
> 
> Offlining and removing an entire region requires operating on individual
> memory blocks, creating race conditions where external entities can
> interfere between the offline and remove steps.
> 
> The problem was discussed specifically in the LPC2025 device memory
> sessions - https://lpc.events/event/19/contributions/2016/ - where
> it was discussed how the non-atomic interface for dax hotplug is causing
> issues in some distributions which have competing userland controllers
> that interfere with each other.
> 
> This series adds a sysfs "hotplug" attribute for atomic whole-device
> hotplug control, along with the mm and dax plumbing to support it.

AI review (which hasn't completed at this time) has a lot to say:
	https://sashiko.dev/#/patchset/20260321150404.3288786-1-gourry@xxxxxxxxxx