On Fri, 16 Oct 2026 21:13:34 +0800 Muchun Song <[email protected]> wrote:
> A compound page of order N must start at a PFN aligned to 2^N pages. > Therefore, a range used to initialize compound pages must start on a > compound-page boundary and contain an integral number of compound pages. > > Two recent Device DAX bugs were caused by ranges that violated this > invariant, but neither was detected by memmap_init_zone_device(). > > Warn if the adjusted zone-device range violates this invariant so future > violations are reported when the compound pages are initialized. > > ... > > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -1142,6 +1142,8 @@ void __ref memmap_init_zone_device(struct zone *zone, > if (!nr_pages) > return; > > + VM_WARN_ON(!IS_ALIGNED(start_pfn | nr_pages, pfns_per_compound)); Would VM_WARN_ON_ONCE() suffice? > + > /* > * Seed the reusable head-page template from the first real struct > * page. The normal page-init and refcount helpers must operate on > > base-commit: 63562804f25cb5b6f5e4f5e3a9f0d1c3c6868596 > -- > 2.54.0
