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> + unsigned long sz = huge_page_size(h); > + struct mm_struct *mm = vma->vm_mm; > + struct mmu_notifier_range range; > + unsigned long address; > + spinlock_t *ptl; > + pte_t *ptep; > + Perhaps we should add a quick to see if vma is sharable. Might be as simple as !(vma->vm_flags & VM_MAYSHARE). I see a comment/question in a later patch about only doing minor fault processing on shared mappings. Code below looks fine, but it would be a wast to do all that for a vma that could not be shared. -- Mike Kravetz > + /* > + * No need to call adjust_range_if_pmd_sharing_possible(), because > + * we're going to operate on the whole vma > + */ > + mmu_notifier_range_init(&range, MMU_NOTIFY_HUGETLB_UNSHARE, > + 0, vma, mm, vma->vm_start, vma->vm_end); > + mmu_notifier_invalidate_range_start(&range); > + i_mmap_lock_write(vma->vm_file->f_mapping); > + for (address = vma->vm_start; address < vma->vm_end; address += sz) { > + ptep = huge_pte_offset(mm, address, sz); > + if (!ptep) > + continue; > + ptl = huge_pte_lock(h, mm, ptep); > + huge_pmd_unshare(mm, vma, &address, ptep); > + spin_unlock(ptl); > + } > + flush_hugetlb_tlb_range(vma, vma->vm_start, vma->vm_end); > + i_mmap_unlock_write(vma->vm_file->f_mapping); > + /* > + * No need to call mmu_notifier_invalidate_range(), see > + * Documentation/vm/mmu_notifier.rst. > + */ > + mmu_notifier_invalidate_range_end(&range); > +#endif > +} > + > static void __wake_userfault(struct userfaultfd_ctx *ctx, > struct userfaultfd_wake_range *range) > { > @@ -1448,6 +1490,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, > vma->vm_flags = new_flags; > vma->vm_userfaultfd_ctx.ctx = ctx; > > + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) > + hugetlb_unshare_all_pmds(vma); > + > skip: > prev = vma; > start = vma->vm_end; > diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h > index b8200782dede..ff50c8528113 100644 > --- a/include/linux/mmu_notifier.h > +++ b/include/linux/mmu_notifier.h > @@ -51,6 +51,7 @@ enum mmu_notifier_event { > MMU_NOTIFY_SOFT_DIRTY, > MMU_NOTIFY_RELEASE, > MMU_NOTIFY_MIGRATE, > + MMU_NOTIFY_HUGETLB_UNSHARE, > }; > > #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0) >