Re: [PATCH v2 4/6] mm/sparse-vmemmap: Pass @pgmap argument to arch vmemmap_populate()

Joao Martins
2026-04-15T12:14:42Z

On 15/04/2026 12:14, Muchun Song wrote:
> Add the struct dev_pagemap pointer as a parameter to the architecture
> specific vmemmap_populate(), vmemmap_populate_hugepages() and
> vmemmap_populate_basepages() functions.
>
> Currently, the vmemmap optimization for DAX is handled mostly in an
> architecture-agnostic way via vmemmap_populate_compound_pages().
> However, this approach skips crucial architecture-specific initialization
> steps. For example, the x86 path must call sync_global_pgds() after
> populating the vmemmap, which is currently being bypassed.
>

Harry's series fixed in a different way (for x86):

https://lore.kernel.org/linux-mm/20250818020206.4517-1-harry.yoo@oracle.com/#t

> To lay the groundwork for fixing the vmemmap optimization in the arch
> level, we need to pass the @pgmap pointer down to the arch specific
> vmemmap_populate() location. Plumb the @pgmap argument through the APIs
> of vmemmap_populate(), vmemmap_populate_hugepages() and
> vmemmap_populate_basepages().
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> arch/arm64/mm/mmu.c | 6 +++---
> arch/loongarch/mm/init.c | 7 ++++---
> arch/powerpc/include/asm/book3s/64/radix.h | 3 ++-
> arch/powerpc/mm/book3s64/radix_pgtable.c | 2 +-
> arch/powerpc/mm/init_64.c | 4 ++--
> arch/riscv/mm/init.c | 4 ++--
> arch/s390/mm/vmem.c | 2 +-
> arch/sparc/mm/init_64.c | 5 +++--
> arch/x86/mm/init_64.c | 8 ++++----
> include/linux/mm.h | 8 +++++---
> mm/hugetlb_vmemmap.c | 4 ++--
> mm/sparse-vmemmap.c | 10 ++++++----
> 12 files changed, 35 insertions(+), 28 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index e5a42b7a0160..11227e104c48 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1790,7 +1790,7 @@ int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
> }
>
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> WARN_ON((start < VMEMMAP_START) || (end > VMEMMAP_END));
> /* [start, end] should be within one section */
> @@ -1798,9 +1798,9 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
>
> if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES) ||
> (end - start < PAGES_PER_SECTION * sizeof(struct page)))
> - return vmemmap_populate_basepages(start, end, node, altmap);
> + return vmemmap_populate_basepages(start, end, node, altmap, pgmap);
> else
> - return vmemmap_populate_hugepages(start, end, node, altmap);
> + return vmemmap_populate_hugepages(start, end, node, altmap, pgmap);
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
> index c9c57f08fa2c..d61c2e09caae 100644
> --- a/arch/loongarch/mm/init.c
> +++ b/arch/loongarch/mm/init.c
> @@ -123,12 +123,13 @@ int __meminit vmemmap_check_pmd(pmd_t *pmd, int node,
> }
>
> int __meminit vmemmap_populate(unsigned long start, unsigned long end,
> - int node, struct vmem_altmap *altmap)
> + int node, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> #if CONFIG_PGTABLE_LEVELS == 2
> - return vmemmap_populate_basepages(start, end, node, NULL);
> + return vmemmap_populate_basepages(start, end, node, NULL, pgmap);
> #else
> - return vmemmap_populate_hugepages(start, end, node, NULL);
> + return vmemmap_populate_hugepages(start, end, node, NULL, pgmap);
> #endif
> }
>
> diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
> index da954e779744..bde07c6f900f 100644
> --- a/arch/powerpc/include/asm/book3s/64/radix.h
> +++ b/arch/powerpc/include/asm/book3s/64/radix.h
> @@ -321,7 +321,8 @@ extern int __meminit radix__vmemmap_create_mapping(unsigned long start,
> unsigned long page_size,
> unsigned long phys);
> int __meminit radix__vmemmap_populate(unsigned long start, unsigned long end,
> - int node, struct vmem_altmap *altmap);
> + int node, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap);
> void __ref radix__vmemmap_free(unsigned long start, unsigned long end,
> struct vmem_altmap *altmap);
> extern void radix__vmemmap_remove_mapping(unsigned long start,
> diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
> index 10aced261cff..568500343e5f 100644
> --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> @@ -1112,7 +1112,7 @@ static inline pte_t *vmemmap_pte_alloc(pmd_t *pmdp, int node,
>
>
> int __meminit radix__vmemmap_populate(unsigned long start, unsigned long end, int node,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> unsigned long addr;
> unsigned long next;
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index b6f3ae03ca9e..8f4aa5b32186 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -275,12 +275,12 @@ static int __meminit __vmemmap_populate(unsigned long start, unsigned long end,
> }
>
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
>
> #ifdef CONFIG_PPC_BOOK3S_64
> if (radix_enabled())
> - return radix__vmemmap_populate(start, end, node, altmap);
> + return radix__vmemmap_populate(start, end, node, altmap, pgmap);
> #endif
>
> return __vmemmap_populate(start, end, node, altmap);
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index b0092fb842a3..a04ae9727cbe 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -1348,7 +1348,7 @@ int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
> }
>
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> WARN_ON((start < VMEMMAP_START) || (end > VMEMMAP_END));
>
> @@ -1358,7 +1358,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> * memory hotplug, we are not able to update all the page tables with
> * the new PMDs.
> */
> - return vmemmap_populate_hugepages(start, end, node, altmap);
> + return vmemmap_populate_hugepages(start, end, node, altmap, pgmap);
> }
> #endif
>
> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
> index eeadff45e0e1..a7bf8d3d5601 100644
> --- a/arch/s390/mm/vmem.c
> +++ b/arch/s390/mm/vmem.c
> @@ -506,7 +506,7 @@ static void vmem_remove_range(unsigned long start, unsigned long size)
> * Add a backed mem_map array to the virtual mem_map array.
> */
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> int ret;
>
> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
> index 367c269305e5..f870ca330f9e 100644
> --- a/arch/sparc/mm/init_64.c
> +++ b/arch/sparc/mm/init_64.c
> @@ -2591,9 +2591,10 @@ int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
> }
>
> int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
> - int node, struct vmem_altmap *altmap)
> + int node, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> - return vmemmap_populate_hugepages(vstart, vend, node, NULL);
> + return vmemmap_populate_hugepages(vstart, vend, node, NULL, pgmap);
> }
> #endif /* CONFIG_SPARSEMEM_VMEMMAP */
>
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 77b889b71cf3..e18cc81a30b4 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1557,7 +1557,7 @@ int __meminit vmemmap_check_pmd(pmd_t *pmd, int node,
> }
>
> int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> int err;
>
> @@ -1565,15 +1565,15 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> VM_BUG_ON(!PAGE_ALIGNED(end));
>
> if (end - start < PAGES_PER_SECTION * sizeof(struct page))
> - err = vmemmap_populate_basepages(start, end, node, NULL);
> + err = vmemmap_populate_basepages(start, end, node, NULL, pgmap);
> else if (boot_cpu_has(X86_FEATURE_PSE))
> - err = vmemmap_populate_hugepages(start, end, node, altmap);
> + err = vmemmap_populate_hugepages(start, end, node, altmap, pgmap);
> else if (altmap) {
> pr_err_once("%s: no cpu support for altmap allocations\n",
> __func__);
> err = -ENOMEM;
> } else
> - err = vmemmap_populate_basepages(start, end, node, NULL);
> + err = vmemmap_populate_basepages(start, end, node, NULL, pgmap);
> if (!err)
> sync_global_pgds(start, end - 1);
> return err;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 0b776907152e..bebc5f892f81 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -4877,11 +4877,13 @@ void vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
> int vmemmap_check_pmd(pmd_t *pmd, int node,
> unsigned long addr, unsigned long next);
> int vmemmap_populate_basepages(unsigned long start, unsigned long end,
> - int node, struct vmem_altmap *altmap);
> + int node, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap);
> int vmemmap_populate_hugepages(unsigned long start, unsigned long end,
> - int node, struct vmem_altmap *altmap);
> + int node, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap);
> int vmemmap_populate(unsigned long start, unsigned long end, int node,
> - struct vmem_altmap *altmap);
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap);
> int vmemmap_populate_hvo(unsigned long start, unsigned long end,
> unsigned int order, struct zone *zone,
> unsigned long headsize);
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 4a077d231d3a..50b7123f3bdd 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -829,7 +829,7 @@ void __init hugetlb_vmemmap_init_late(int nid)
> */
> list_del(&m->list);
>
> - vmemmap_populate(start, end, nid, NULL);
> + vmemmap_populate(start, end, nid, NULL, NULL);
> nr_mmap = end - start;
> memmap_boot_pages_add(DIV_ROUND_UP(nr_mmap, PAGE_SIZE));
>
> @@ -845,7 +845,7 @@ void __init hugetlb_vmemmap_init_late(int nid)
> if (vmemmap_populate_hvo(start, end, huge_page_order(h), zone,
> HUGETLB_VMEMMAP_RESERVE_SIZE) < 0) {
> /* Fallback if HVO population fails */
> - vmemmap_populate(start, end, nid, NULL);
> + vmemmap_populate(start, end, nid, NULL, NULL);
> nr_mmap = end - start;
> } else {
> m->flags |= HUGE_BOOTMEM_ZONES_VALID;
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 05e3e2b94e32..f5245647afee 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -297,7 +297,8 @@ static int __meminit vmemmap_populate_range(unsigned long start,
> }
>
> int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
> - int node, struct vmem_altmap *altmap)
> + int node, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> return vmemmap_populate_range(start, end, node, altmap, -1, 0);
> }
> @@ -400,7 +401,8 @@ int __weak __meminit vmemmap_check_pmd(pmd_t *pmd, int node,
> }
>
> int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
> - int node, struct vmem_altmap *altmap)
> + int node, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> unsigned long addr;
> unsigned long next;
> @@ -445,7 +447,7 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
> }
> } else if (vmemmap_check_pmd(pmd, node, addr, next))
> continue;
> - if (vmemmap_populate_basepages(addr, next, node, altmap))
> + if (vmemmap_populate_basepages(addr, next, node, altmap, pgmap))
> return -ENOMEM;
> }
> return 0;
> @@ -559,7 +561,7 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn,
> if (vmemmap_can_optimize(altmap, pgmap))
> r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap);
> else
> - r = vmemmap_populate(start, end, nid, altmap);
> + r = vmemmap_populate(start, end, nid, altmap, pgmap);
>
> if (r < 0)
> return NULL;