The patch titled Subject: mm: fix accounting of memmap pages has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-fix-accounting-of-memmap-pages.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Sumanth Korikkar sumanthk@linux.ibm.com Subject: mm: fix accounting of memmap pages Date: Thu, 7 Aug 2025 20:35:45 +0200

For !CONFIG_SPARSEMEM_VMEMMAP, memmap page accounting is currently done upfront in sparse_buffer_init(). However, sparse_buffer_alloc() may return NULL in failure scenario.

Also, memmap pages may be allocated either from the memblock allocator during early boot or from the buddy allocator. When removed via arch_remove_memory(), accounting of memmap pages must reflect the original allocation source.

To ensure correctness: * Account memmap pages after successful allocation in sparse_init_nid() and section_activate(). * Account memmap pages in section_deactivate() based on allocation source.

Link: https://lkml.kernel.org/r/20250807183545.1424509-1-sumanthk@linux.ibm.com Fixes: 15995a352474 ("mm: report per-page metadata information") Signed-off-by: Sumanth Korikkar sumanthk@linux.ibm.com Suggested-by: David Hildenbrand david@redhat.com Cc: Alexander Gordeev agordeev@linux.ibm.com Cc: Gerald Schaefer gerald.schaefer@linux.ibm.com Cc: Heiko Carstens hca@linux.ibm.com Cc: Vasily Gorbik gor@linux.ibm.com Cc: Wei Yang richard.weiyang@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/sparse-vmemmap.c | 5 ----- mm/sparse.c | 15 +++++++++------ 2 files changed, 9 insertions(+), 11 deletions(-)

--- a/mm/sparse.c~mm-fix-accounting-of-memmap-pages +++ a/mm/sparse.c @@ -454,9 +454,6 @@ static void __init sparse_buffer_init(un */ sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid, true); sparsemap_buf_end = sparsemap_buf + size; -#ifndef CONFIG_SPARSEMEM_VMEMMAP - memmap_boot_pages_add(DIV_ROUND_UP(size, PAGE_SIZE)); -#endif }

static void __init sparse_buffer_fini(void) @@ -567,6 +564,8 @@ static void __init sparse_init_nid(int n sparse_buffer_fini(); goto failed; } + memmap_boot_pages_add(DIV_ROUND_UP(PAGES_PER_SECTION * sizeof(struct page), + PAGE_SIZE)); sparse_init_early_section(nid, map, pnum, 0); } } @@ -680,7 +679,6 @@ static void depopulate_section_memmap(un unsigned long start = (unsigned long) pfn_to_page(pfn); unsigned long end = start + nr_pages * sizeof(struct page);

- memmap_pages_add(-1L * (DIV_ROUND_UP(end - start, PAGE_SIZE))); vmemmap_free(start, end, altmap); } static void free_map_bootmem(struct page *memmap) @@ -857,10 +855,14 @@ static void section_deactivate(unsigned * The memmap of early sections is always fully populated. See * section_activate() and pfn_valid() . */ - if (!section_is_early) + if (!section_is_early) { + memmap_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE))); depopulate_section_memmap(pfn, nr_pages, altmap); - else if (memmap) + } else if (memmap) { + memmap_boot_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), + PAGE_SIZE))); free_map_bootmem(memmap); + }

if (empty) ms->section_mem_map = (unsigned long)NULL; @@ -905,6 +907,7 @@ static struct page * __meminit section_a section_deactivate(pfn, nr_pages, altmap); return ERR_PTR(-ENOMEM); } + memmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE));

return memmap; } --- a/mm/sparse-vmemmap.c~mm-fix-accounting-of-memmap-pages +++ a/mm/sparse-vmemmap.c @@ -578,11 +578,6 @@ struct page * __meminit __populate_secti if (r < 0) return NULL;

- if (system_state == SYSTEM_BOOTING) - memmap_boot_pages_add(DIV_ROUND_UP(end - start, PAGE_SIZE)); - else - memmap_pages_add(DIV_ROUND_UP(end - start, PAGE_SIZE)); - return pfn_to_page(pfn); }

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Patches currently in -mm which might be from sumanthk@linux.ibm.com are

mm-fix-accounting-of-memmap-pages-for-early-sections.patch mm-fix-accounting-of-memmap-pages.patch