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Sun, 05 Apr 2026 05:53:40 -0700 (PDT) From: Muchun Song To: Andrew Morton , David Hildenbrand , Muchun Song , Oscar Salvador , Michael Ellerman , Madhavan Srinivasan Cc: Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Muchun Song Subject: [PATCH 03/49] mm/sparse: fix vmemmap page accounting for HVOed DAX Date: Sun, 5 Apr 2026 20:51:54 +0800 Message-Id: <20260405125240.2558577-4-songmuchun@bytedance.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20260405125240.2558577-1-songmuchun@bytedance.com> References: <20260405125240.2558577-1-songmuchun@bytedance.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When HVO is enabled for DAX, the vmemmap page accounting is wrong since it only accounts for non-HVO case. Fix the accounting by introducing section_vmemmap_pages() that returns the exact number of vmemmap pages needed for the given pfn range. Fixes: 15995a352474 ("mm: report per-page metadata information") Signed-off-by: Muchun Song --- mm/sparse-vmemmap.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index 7aa9a97498eb..0ef96b1afbcc 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -724,6 +724,27 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages) return rc; } +static int __meminit section_vmemmap_pages(unsigned long pfn, unsigned long nr_pages, + struct vmem_altmap *altmap, struct dev_pagemap *pgmap) +{ + unsigned int order = pgmap ? pgmap->vmemmap_shift : 0; + unsigned long pages_per_compound = 1L << order; + + VM_BUG_ON(!IS_ALIGNED(pfn | nr_pages, min(pages_per_compound, PAGES_PER_SECTION))); + VM_BUG_ON(pfn_to_section_nr(pfn) != pfn_to_section_nr(pfn + nr_pages - 1)); + + if (!vmemmap_can_optimize(altmap, pgmap)) + return DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE); + + if (order < PFN_SECTION_SHIFT) + return VMEMMAP_RESERVE_NR * nr_pages / pages_per_compound; + + if (IS_ALIGNED(pfn, pages_per_compound)) + return VMEMMAP_RESERVE_NR; + + return 0; +} + /* * To deactivate a memory region, there are 3 cases to handle: * @@ -775,11 +796,12 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, * section_activate() and pfn_valid() . */ if (!section_is_early) { - memmap_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE))); + memmap_pages_add(-section_vmemmap_pages(pfn, nr_pages, altmap, + pgmap)); depopulate_section_memmap(pfn, nr_pages, altmap); } else if (memmap) { - memmap_boot_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), - PAGE_SIZE))); + memmap_pages_add(-section_vmemmap_pages(pfn, nr_pages, altmap, + pgmap)); free_map_bootmem(memmap); } @@ -822,7 +844,7 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn, return pfn_to_page(pfn); memmap = populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap); - memmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE)); + memmap_pages_add(section_vmemmap_pages(pfn, nr_pages, altmap, pgmap)); if (!memmap) { section_deactivate(pfn, nr_pages, altmap, pgmap); return ERR_PTR(-ENOMEM); -- 2.20.1