Re: [PATCH v3 0/8] mm: fix allocator races with memory hotplug

[David Hildenbrand (Arm)]

On 10/21/26 04:39, Gregory Price (Meta) wrote:
> Eight fixes for allocator paths that can act on state another CPU is
> updating: zonelists rebuilt by memory hotplug, and the pagesets of a
> zone that offlining empties.
> 
> I've packaged these together because they're all related to hotplug.
> 
> *** Backport note - Patches 5-7 build on patch 1: without it, their
>     retry is compiled out when CONFIG_MEMORY_HOTREMOVE=n.
> 
> Most of these race conditions stem from zonelists being re-ordered
> in-place at runtime during hotplug.  The result is a mixture of failed
> allocations, NULL dereferences, incorrect placement (GFP_KERNEL in
> ZONE_MOVABLE), node misplacement, or incorrectly allowing hugetlb /
> contig allocations on a node/zone otherwise not eligible.
> 
> Most of these are incredibly narrow race conditions, but since the most
> likely impacted machines are VMs with memory hotplug, the narrow
> condition can more easily occur when a vCPU takes a long interrupt / VM
> exit of some kind.  I've made all of these race conditions
> deterministics with a kprobe reproduction module described below.

What's the status of this? "memory hotplug" caught my attention, but then then
is all page_alloc material :)

-- 
Cheers,

David