From: David Hildenbrand (Arm) Date: Mon, 9 Mar 2026 15:18:58 +0000 (+0100) Subject: mm: move vma_kernel_pagesize() from hugetlb to mm.h X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=341ffe82a7a3a1e0756b58999405b6df0c2b3e8d;p=thirdparty%2Flinux.git mm: move vma_kernel_pagesize() from hugetlb to mm.h Patch series "mm: move vma_(kernel|mmu)_pagesize() out of hugetlb.c", v2. Looking into vma_(kernel|mmu)_pagesize(), I realized that there is one scenario where DAX would not do the right thing when the kernel is not compiled with hugetlb support. Without hugetlb support, vma_(kernel|mmu)_pagesize() will always return PAGE_SIZE instead of using the ->pagesize() result provided by dax-device code. Fix that by moving vma_kernel_pagesize() to core MM code, where it belongs. I don't think this is stable material, but am not 100% sure. Also, move vma_mmu_pagesize() while at it. Remove the unnecessary hugetlb.h inclusion from KVM code. This patch (of 4): In the past, only hugetlb had special "vma_kernel_pagesize()" requirements, so it provided its own implementation. In commit 05ea88608d4e ("mm, hugetlbfs: introduce ->pagesize() to vm_operations_struct") we generalized that approach by providing a vm_ops->pagesize() callback to be used by device-dax. Once device-dax started using that callback in commit c1d53b92b95c ("device-dax: implement ->pagesize() for smaps to report MMUPageSize") it was missed that CONFIG_DEV_DAX does not depend on hugetlb support. So building a kernel with CONFIG_DEV_DAX but without CONFIG_HUGETLBFS would not pick up that value. Fix it by moving vma_kernel_pagesize() to mm.h, providing only a single implementation. While at it, improve the kerneldoc a bit. Ideally, we'd move vma_mmu_pagesize() as well to the header. However, its __weak symbol might be overwritten by a PPC variant in hugetlb code. So let's leave it in there for now, as it really only matters for some hugetlb oddities. This was found by code inspection. Link: https://lkml.kernel.org/r/20260309151901.123947-1-david@kernel.org Link: https://lkml.kernel.org/r/20260309151901.123947-2-david@kernel.org Fixes: c1d53b92b95c ("device-dax: implement ->pagesize() for smaps to report MMUPageSize") Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (Oracle) Acked-by: Mike Rapoport (Microsoft) Cc: Dan Williams Cc: "Christophe Leroy (CS GROUP)" Cc: Jann Horn Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Muchun Song Cc: Nicholas Piggin Cc: Oscar Salvador Cc: Paolo Bonzini Cc: Pedro Falcato Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 65910437be1ca..44c1848a2c216 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -777,8 +777,6 @@ static inline unsigned long huge_page_size(const struct hstate *h) return (unsigned long)PAGE_SIZE << h->order; } -extern unsigned long vma_kernel_pagesize(struct vm_area_struct *vma); - extern unsigned long vma_mmu_pagesize(struct vm_area_struct *vma); static inline unsigned long huge_page_mask(struct hstate *h) @@ -1177,11 +1175,6 @@ static inline unsigned long huge_page_mask(struct hstate *h) return PAGE_MASK; } -static inline unsigned long vma_kernel_pagesize(struct vm_area_struct *vma) -{ - return PAGE_SIZE; -} - static inline unsigned long vma_mmu_pagesize(struct vm_area_struct *vma) { return PAGE_SIZE; diff --git a/include/linux/mm.h b/include/linux/mm.h index c758f4e687278..e62cea754b0ec 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1351,6 +1351,26 @@ static inline bool vma_is_shared_maywrite(const struct vm_area_struct *vma) return is_shared_maywrite(&vma->flags); } +/** + * vma_kernel_pagesize - Default page size granularity for this VMA. + * @vma: The user mapping. + * + * The kernel page size specifies in which granularity VMA modifications + * can be performed. Folios in this VMA will be aligned to, and at least + * the size of the number of bytes returned by this function. + * + * The default kernel page size is not affected by Transparent Huge Pages + * being in effect. + * + * Return: The default page size granularity for this VMA. + */ +static inline unsigned long vma_kernel_pagesize(struct vm_area_struct *vma) +{ + if (unlikely(vma->vm_ops && vma->vm_ops->pagesize)) + return vma->vm_ops->pagesize(vma); + return PAGE_SIZE; +} + static inline struct vm_area_struct *vma_find(struct vma_iterator *vmi, unsigned long max) { diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 992c1632d26ab..66761ae5ce710 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1017,23 +1017,6 @@ static pgoff_t vma_hugecache_offset(struct hstate *h, (vma->vm_pgoff >> huge_page_order(h)); } -/** - * vma_kernel_pagesize - Page size granularity for this VMA. - * @vma: The user mapping. - * - * Folios in this VMA will be aligned to, and at least the size of the - * number of bytes returned by this function. - * - * Return: The default size of the folios allocated when backing a VMA. - */ -unsigned long vma_kernel_pagesize(struct vm_area_struct *vma) -{ - if (vma->vm_ops && vma->vm_ops->pagesize) - return vma->vm_ops->pagesize(vma); - return PAGE_SIZE; -} -EXPORT_SYMBOL_GPL(vma_kernel_pagesize); - /* * Return the page size being used by the MMU to back a VMA. In the majority * of cases, the page size used by the kernel matches the MMU size. On