On 04.02.25 23:48, Alistair Popple wrote:
Currently to map a DAX page the DAX driver calls vmf_insert_pfn. This creates a special devmap PTE entry for the pfn but does not take a reference on the underlying struct page for the mapping. This is because DAX page refcounts are treated specially, as indicated by the presence of a devmap entry.To allow DAX page refcounts to be managed the same as normal page refcounts introduce vmf_insert_page_mkwrite(). This will take a reference on the underlying page much the same as vmf_insert_page, except it also permits upgrading an existing mapping to be writable if requested/possible. Signed-off-by: Alistair Popple <apop...@nvidia.com> --- Changes for v7: - Fix vmf_insert_page_mkwrite by removing pfn gunk as suggested by David. Updates from v2: - Rename function to make not DAX specific - Split the insert_page_into_pte_locked() change into a separate patch. Updates from v1: - Re-arrange code in insert_page_into_pte_locked() based on comments from Jan Kara. - Call mkdrity/mkyoung for the mkwrite case, also suggested by Jan. --- include/linux/mm.h | 2 ++ mm/memory.c | 21 +++++++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 7b1068d..6567ece 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3544,6 +3544,8 @@ int vm_map_pages(struct vm_area_struct *vma, struct page **pages, unsigned long num); int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages, unsigned long num); +vm_fault_t vmf_insert_page_mkwrite(struct vm_fault *vmf, struct page *page, + bool write); vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn); vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, diff --git a/mm/memory.c b/mm/memory.c index 41befd9..b88b488 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2622,6 +2622,27 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma, return VM_FAULT_NOPAGE; }+vm_fault_t vmf_insert_page_mkwrite(struct vm_fault *vmf, struct page *page,+ bool write) +{ + struct vm_area_struct *vma = vmf->vma; + pgprot_t pgprot = vma->vm_page_prot;
Probably could have avoided that temp without harming readability Acked-by: David Hildenbrand <da...@redhat.com> -- Cheers, David / dhildenb
