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

[Joao Martins]

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@xxxxxxxxxx/#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@xxxxxxxxxxxxx>
> ---
>  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;