On Thu, Aug 28, 2025 at 12:01:15AM +0200, David Hildenbrand wrote:
Let's limit the maximum folio size in problematic kernel config where the memmap is allocated per memory section (SPARSEMEM without SPARSEMEM_VMEMMAP) to a single memory section.
Currently, only a single architectures supports ARCH_HAS_GIGANTIC_PAGE but not SPARSEMEM_VMEMMAP: sh.
Fortunately, the biggest hugetlb size sh supports is 64 MiB (HUGETLB_PAGE_SIZE_64MB) and the section size is at least 64 MiB (SECTION_SIZE_BITS == 26), so their use case is not degraded.
As folios and memory sections are naturally aligned to their order-2 size in memory, consequently a single folio can no longer span multiple memory sections on these problematic kernel configs.
nth_page() is no longer required when operating within a single compound page / folio.
Reviewed-by: Zi Yan ziy@nvidia.com Acked-by: Mike Rapoport (Microsoft) rppt@kernel.org Signed-off-by: David Hildenbrand david@redhat.com
Reviewed-by: Wei Yang richard.weiyang@gmail.com