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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 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 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4a32106e-d821-48f2-d5a0-08dcd14f2e4b X-MS-Exchange-CrossTenant-AuthSource: DS0PR12MB7726.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Sep 2024 04:15:19.2031 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: vrD+oo8TgBdRf5WfNZocgy7YpSi09mpOuFvt+6m/W4jpWAksLIQ49wwxXSOW4YqO+Kh9BVzpdCHqpFjQ8xteYw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4148 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 dax_insert_pfn. 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 Signed-off-by: Dan Williams --- 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 | 1 +- mm/memory.c | 83 ++++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 76 insertions(+), 8 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index b0ff06d..ae6d713 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3463,6 +3463,7 @@ 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 dax_insert_pfn(struct vm_fault *vmf, pfn_t pfn_t, 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 d2785fb..368e15d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2039,19 +2039,47 @@ static int validate_page_before_insert(struct vm_area_struct *vma, } static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte, - unsigned long addr, struct page *page, pgprot_t prot) + unsigned long addr, struct page *page, + pgprot_t prot, bool mkwrite) { struct folio *folio = page_folio(page); + pte_t entry = ptep_get(pte); pte_t pteval; - if (!pte_none(ptep_get(pte))) - return -EBUSY; + if (!pte_none(entry)) { + if (!mkwrite) + return -EBUSY; + + /* + * For read faults on private mappings the PFN passed in may not + * match the PFN we have mapped if the mapped PFN is a writeable + * COW page. In the mkwrite case we are creating a writable PTE + * for a shared mapping and we expect the PFNs to match. If they + * don't match, we are likely racing with block allocation and + * mapping invalidation so just skip the update. + */ + if (pte_pfn(entry) != page_to_pfn(page)) { + WARN_ON_ONCE(!is_zero_pfn(pte_pfn(entry))); + return -EFAULT; + } + entry = maybe_mkwrite(entry, vma); + entry = pte_mkyoung(entry); + if (ptep_set_access_flags(vma, addr, pte, entry, 1)) + update_mmu_cache(vma, addr, pte); + return 0; + } + /* Ok, finally just insert the thing.. */ pteval = mk_pte(page, prot); if (unlikely(is_zero_folio(folio))) { pteval = pte_mkspecial(pteval); } else { folio_get(folio); + entry = mk_pte(page, prot); + if (mkwrite) { + entry = pte_mkyoung(entry); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + } inc_mm_counter(vma->vm_mm, mm_counter_file(folio)); folio_add_file_rmap_pte(folio, page, vma); } @@ -2060,7 +2088,7 @@ static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte, } static int insert_page(struct vm_area_struct *vma, unsigned long addr, - struct page *page, pgprot_t prot) + struct page *page, pgprot_t prot, bool mkwrite) { int retval; pte_t *pte; @@ -2073,7 +2101,8 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr, pte = get_locked_pte(vma->vm_mm, addr, &ptl); if (!pte) goto out; - retval = insert_page_into_pte_locked(vma, pte, addr, page, prot); + retval = insert_page_into_pte_locked(vma, pte, addr, page, prot, + mkwrite); pte_unmap_unlock(pte, ptl); out: return retval; @@ -2087,7 +2116,7 @@ static int insert_page_in_batch_locked(struct vm_area_struct *vma, pte_t *pte, err = validate_page_before_insert(vma, page); if (err) return err; - return insert_page_into_pte_locked(vma, pte, addr, page, prot); + return insert_page_into_pte_locked(vma, pte, addr, page, prot, false); } /* insert_pages() amortizes the cost of spinlock operations @@ -2223,7 +2252,7 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, BUG_ON(vma->vm_flags & VM_PFNMAP); vm_flags_set(vma, VM_MIXEDMAP); } - return insert_page(vma, addr, page, vma->vm_page_prot); + return insert_page(vma, addr, page, vma->vm_page_prot, false); } EXPORT_SYMBOL(vm_insert_page); @@ -2503,7 +2532,7 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma, * result in pfn_t_has_page() == false. */ page = pfn_to_page(pfn_t_to_pfn(pfn)); - err = insert_page(vma, addr, page, pgprot); + err = insert_page(vma, addr, page, pgprot, mkwrite); } else { return insert_pfn(vma, addr, pfn, pgprot, mkwrite); } @@ -2516,6 +2545,44 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma, return VM_FAULT_NOPAGE; } +vm_fault_t dax_insert_pfn(struct vm_fault *vmf, pfn_t pfn_t, bool write) +{ + struct vm_area_struct *vma = vmf->vma; + pgprot_t pgprot = vma->vm_page_prot; + unsigned long pfn = pfn_t_to_pfn(pfn_t); + struct page *page = pfn_to_page(pfn); + unsigned long addr = vmf->address; + int err; + + if (addr < vma->vm_start || addr >= vma->vm_end) + return VM_FAULT_SIGBUS; + + track_pfn_insert(vma, &pgprot, pfn_t); + + if (!pfn_modify_allowed(pfn, pgprot)) + return VM_FAULT_SIGBUS; + + /* + * We refcount the page normally so make sure pfn_valid is true. + */ + if (!pfn_t_valid(pfn_t)) + return VM_FAULT_SIGBUS; + + WARN_ON_ONCE(pfn_t_devmap(pfn_t)); + + if (WARN_ON(is_zero_pfn(pfn) && write)) + return VM_FAULT_SIGBUS; + + err = insert_page(vma, addr, page, pgprot, write); + if (err == -ENOMEM) + return VM_FAULT_OOM; + if (err < 0 && err != -EBUSY) + return VM_FAULT_SIGBUS; + + return VM_FAULT_NOPAGE; +} +EXPORT_SYMBOL_GPL(dax_insert_pfn); + vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr, pfn_t pfn) {