kernel/git/next/linux-next.git/mm/sparse.h, branch master

mm/hugetlb: switch HugeTLB to section-based vmemmap optimization

2026-09-11T03:20:04+00:00

HugeTLB bootmem vmemmap optimization still carries its own early setup path, including pre-populating optimized mappings before the generic sparse-vmemmap code runs. Now that the section-based vmemmap optimization can derive HugeTLB vmemmap deduplication from section metadata, HugeTLB only needs to mark the bootmem huge page range with the appropriate order. The generic sparse-vmemmap population path can then allocate and map the shared tail vmemmap pages without any HugeTLB-specific early population code. Do that by recording the compound page order when a bootmem huge page is allocated and dropping the dedicated pre-HVO helpers and related special-casing. This removes duplicate early setup logic and switches HugeTLB to the section-based vmemmap optimization path. Link: https://lore.kernel.org/20260910063256.64386-11-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Mike Rapoport (Microsoft) Acked-by: Qi Zheng Cc: David Hildenbrand (Arm) Cc: David Laight Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Oscar Salvador Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/sparse: initialize memory sections earlier

2026-09-11T03:20:04+00:00

Upcoming HugeTLB bootmem changes need sparsemem section metadata before the HugeTLB bootmem allocation path runs. The memory sections are initialized from sparse_init(), which is called too late for that setup. Move the code that initializes sparsemem section metadata for memblock ranges into mm_core_init_early(), before free_area_init() and the HugeTLB bootmem setup. Rename the helper to sparse_sections_init() so the new caller describes the sparsemem-specific initialization step. This is a preparatory change. Link: https://lore.kernel.org/20260910063256.64386-10-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Mike Rapoport (Microsoft) Acked-by: Qi Zheng Cc: David Hildenbrand (Arm) Cc: David Laight Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Oscar Salvador Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/sparse-vmemmap: support section-based vmemmap optimization

2026-09-11T03:20:04+00:00

Teach sparse-vmemmap population code to use the compound page order when deciding whether a vmemmap page can be optimized. With this information, the common sparse-vmemmap population path can allocate or reuse shared tail vmemmap pages directly instead of relying on HugeTLB-specific handling. This centralizes vmemmap optimization logic in the sparse-vmemmap code, based on section metadata, and prepares for sharing the same mechanism across different users of vmemmap optimization, including HugeTLB and DAX. Link: https://lore.kernel.org/20260910063256.64386-9-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Mike Rapoport (Microsoft) Acked-by: Qi Zheng Cc: David Hildenbrand (Arm) Cc: David Laight Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Oscar Salvador Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/sparse-vmemmap: support section-based vmemmap accounting

2026-09-11T03:20:03+00:00

section_nr_vmemmap_pages() can account ordinary sections and DAX sections, but section-based vmemmap optimization stores the compound page order in struct mem_section and retains a different number of vmemmap pages. Teach section_nr_vmemmap_pages() to recognize section-based optimized sections and calculate their vmemmap page count from the stored compound page order and the HVO retained page count. Link: https://lore.kernel.org/20260910063256.64386-6-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Mike Rapoport (Microsoft) Acked-by: Qi Zheng Cc: David Hildenbrand (Arm) Cc: David Laight Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Oscar Salvador Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/mm_init: skip initializing shared vmemmap tail pages

2026-09-11T03:20:02+00:00

memmap_init_range() initializes every struct page in the target range. For compound pages with vmemmap optimization, the tail struct pages are backed by a shared vmemmap page. Initializing those tail struct pages would overwrite the shared vmemmap page contents, requiring users such as HugeTLB to restore the metadata afterwards. Track the compound page order for HVO-backed sections and use that metadata to detect struct pages that fall into the shared tail vmemmap range. Skip those shared tail pages in memmap_init_range(), then initialize pageblock migratetypes for the processed range with a helper after the per-page initialization loop. Keep direct mem_section access inside sparse helpers. Expose pfn_to_section_compound_order() for callers that only need the order associated with a PFN. This lets memmap_init_range() skip shared tail vmemmap pages without exposing __pfn_to_section() to !SPARSEMEM builds. This is a preparatory change for consolidating handling across users of vmemmap optimization, and it also avoids redundant initialization of shared tail vmemmap pages during early boot. That early-boot benefit appears only once HugeTLB is switched to this common handling, since HugeTLB is the early-boot user that creates those shared tail vmemmap pages. Link: https://lore.kernel.org/20260910063256.64386-4-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Mike Rapoport (Microsoft) Acked-by: Qi Zheng Cc: David Hildenbrand (Arm) Cc: David Laight Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Oscar Salvador Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/sparse: keep mem_section_usage_size() internal

2026-08-25T01:43:06+00:00

mem_section_usage_size() is only needed by sparsemem implementation code after commit ae751d567baa ("mm/bootmem_info: stop marking mem_section_usage as MIX_SECTION_INFO"), so keeping the declaration in mmzone.h now exposes the helper to all mmzone.h users for no reason. Move the helper to sparse.h so sparse.c and sparse-vmemmap.c can share it through the internal header. While doing so, calculate the allocation size with struct_size_t(), which ties the expression to the pageblock_flags trailing array instead of open-coding the struct header plus bitmap size. Link: https://lore.kernel.org/20260805022536.1206575-1-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Mike Rapoport (Microsoft) Acked-by: David Hildenbrand (Arm) Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm: split out sparse declarations from internal.h

2026-08-05T02:18:46+00:00

mm/internal.h becomes more and more bloated. Move declarations related to SPARSE and SPARSE_VMEMMAP memory models to a new mm/sparse.h header. No functional changes. Link: https://lore.kernel.org/20260709-internal-h-v2-2-695631425968@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Acked-by: Muchun Song Acked-by: Vlastimil Babka (SUSE) Acked-by: David Hildenbrand (Arm) Acked-by: Lorenzo Stoakes Acked-by: Pratyush Yadav Acked-by: SJ Park Cc: Alexander Graf Cc: Alexander Potapenko Cc: Brendan Jackman Cc: Brendan Jackman Cc: Dennis Zhou Cc: Dmitry Vyukov Cc: Johannes Weiner Cc: Liam R. Howlett Cc: Marco Elver Cc: Michal Hocko Cc: Oscar Salvador Cc: Pasha Tatashin Cc: Suren Baghdasaryan Cc: Tejun Heo Cc: "Uladzislau Rezki (Sony)" Cc: Zi Yan Signed-off-by: Andrew Morton