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This does not work for pages that were allocated via __get_user_pages and then mapped to user-space via remap_pfn_rage. remap_pfn_range_internal() will turn on VM_IO | VM_PFNMAP vma bits. VM_PFNMAP in particular mark the pages as not having struct_page associated with them, which is not the case for __get_user_pages() This in turn makes any attempt to lock a page fail, and breaking I/O from that address range. This patch address it by special casing pages in those VMAs and not calling vm_normal_page() for them. Signed-off-by: Pantelis Antoniou --- mm/gup.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 84461d384ae2..e185c18c0c81 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -833,6 +833,20 @@ static inline bool can_follow_write_pte(pte_t pte, struct page *page, return !userfaultfd_pte_wp(vma, pte); } +static struct page *gup_normal_page(struct vm_area_struct *vma, + unsigned long address, pte_t pte) +{ + unsigned long pfn; + + if (vma->vm_flags & (VM_MIXEDMAP | VM_PFNMAP)) { + pfn = pte_pfn(pte); + if (!pfn_valid(pfn) || is_zero_pfn(pfn) || pfn > highest_memmap_pfn) + return NULL; + return pfn_to_page(pfn); + } + return vm_normal_page(vma, address, pte); +} + static struct page *follow_page_pte(struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, unsigned int flags, struct dev_pagemap **pgmap) @@ -858,7 +872,9 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, if (pte_protnone(pte) && !gup_can_follow_protnone(vma, flags)) goto no_page; - page = vm_normal_page(vma, address, pte); + page = gup_normal_page(vma, address, pte); + if (page && (vma->vm_flags & (VM_MIXEDMAP | VM_PFNMAP))) + (void)follow_pfn_pte(vma, address, ptep, flags); /* * We only care about anon pages in can_follow_write_pte() and don't @@ -1130,7 +1146,7 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address, *vma = get_gate_vma(mm); if (!page) goto out; - *page = vm_normal_page(*vma, address, entry); + *page = gup_normal_page(*vma, address, entry); if (!*page) { if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(entry))) goto unmap; @@ -1271,8 +1287,6 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) int foreign = (gup_flags & FOLL_REMOTE); bool vma_anon = vma_is_anonymous(vma); - if (vm_flags & (VM_IO | VM_PFNMAP)) - return -EFAULT; if ((gup_flags & FOLL_ANON) && !vma_anon) return -EFAULT; -- 2.25.1