On Fri, 2025-04-25 at 22:12 +0200, David Hildenbrand wrote:
> 
> In any case, trying to figure out why Lorenzo ran into an issue ... if 
> it's nit because of the pageblock, maybe something in for_each_valid_pfn 
> with sparsemem is still shaky.

Yep, I think this was it:

--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -2190,10 +2190,10 @@ static inline unsigned long next_valid_pfn(unsigned long pfn, unsigned long end_
        /*
         * Either every PFN within the section (or subsection for VMEMMAP) is
         * valid, or none of them are. So there's no point repeating the check
-        * for every PFN; only call first_valid_pfn() the first time, and when
-        * crossing a (sub)section boundary (i.e. !(pfn & ~PFN_VALID_MASK)).
+        * for every PFN; only call first_valid_pfn() again when crossing a
+        * (sub)section boundary (i.e. !(pfn & ~PAGE_{SUB,}SECTION_MASK)).
         */
-       if (pfn & (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) ?
+       if (pfn & ~(IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) ?
                   PAGE_SUBSECTION_MASK : PAGE_SECTION_MASK))
                return pfn;
 
I've pushed the fixed version out to 
https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/for_each_valid_pfn