From 8fb5debc5fcd450470cdd789c2d80ef95ebb8cf4 Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Wed, 22 Feb 2017 15:42:52 -0800 Subject: [PATCH] userfaultfd: hugetlbfs: add hugetlb_mcopy_atomic_pte for userfaultfd support hugetlb_mcopy_atomic_pte is the low level routine that implements the userfaultfd UFFDIO_COPY command. It is based on the existing mcopy_atomic_pte routine with modifications for huge pages. Link: http://lkml.kernel.org/r/20161216144821.5183-18-aarcange@redhat.com Signed-off-by: Mike Kravetz Signed-off-by: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Hillf Danton Cc: Michael Rapoport Cc: Mike Rapoport Cc: Pavel Emelyanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/hugetlb.h | 7 ++++ mm/hugetlb.c | 81 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 88 insertions(+) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 48c76d612d40..aab2fff3e269 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -81,6 +81,11 @@ void hugetlb_show_meminfo(void); unsigned long hugetlb_total_pages(void); int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, unsigned int flags); +int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, pte_t *dst_pte, + struct vm_area_struct *dst_vma, + unsigned long dst_addr, + unsigned long src_addr, + struct page **pagep); int hugetlb_reserve_pages(struct inode *inode, long from, long to, struct vm_area_struct *vma, vm_flags_t vm_flags); @@ -149,6 +154,8 @@ static inline void hugetlb_show_meminfo(void) #define is_hugepage_only_range(mm, addr, len) 0 #define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) ({BUG(); 0; }) #define hugetlb_fault(mm, vma, addr, flags) ({ BUG(); 0; }) +#define hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma, dst_addr, \ + src_addr, pagep) ({ BUG(); 0; }) #define huge_pte_offset(mm, address) 0 static inline int dequeue_hwpoisoned_huge_page(struct page *page) { diff --git a/mm/hugetlb.c b/mm/hugetlb.c index c7025c132670..dec628b26f59 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3948,6 +3948,87 @@ out_mutex: return ret; } +/* + * Used by userfaultfd UFFDIO_COPY. Based on mcopy_atomic_pte with + * modifications for huge pages. + */ +int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, + pte_t *dst_pte, + struct vm_area_struct *dst_vma, + unsigned long dst_addr, + unsigned long src_addr, + struct page **pagep) +{ + struct hstate *h = hstate_vma(dst_vma); + pte_t _dst_pte; + spinlock_t *ptl; + int ret; + struct page *page; + + if (!*pagep) { + ret = -ENOMEM; + page = alloc_huge_page(dst_vma, dst_addr, 0); + if (IS_ERR(page)) + goto out; + + ret = copy_huge_page_from_user(page, + (const void __user *) src_addr, + pages_per_huge_page(h)); + + /* fallback to copy_from_user outside mmap_sem */ + if (unlikely(ret)) { + ret = -EFAULT; + *pagep = page; + /* don't free the page */ + goto out; + } + } else { + page = *pagep; + *pagep = NULL; + } + + /* + * The memory barrier inside __SetPageUptodate makes sure that + * preceding stores to the page contents become visible before + * the set_pte_at() write. + */ + __SetPageUptodate(page); + set_page_huge_active(page); + + ptl = huge_pte_lockptr(h, dst_mm, dst_pte); + spin_lock(ptl); + + ret = -EEXIST; + if (!huge_pte_none(huge_ptep_get(dst_pte))) + goto out_release_unlock; + + ClearPagePrivate(page); + hugepage_add_new_anon_rmap(page, dst_vma, dst_addr); + + _dst_pte = make_huge_pte(dst_vma, page, dst_vma->vm_flags & VM_WRITE); + if (dst_vma->vm_flags & VM_WRITE) + _dst_pte = huge_pte_mkdirty(_dst_pte); + _dst_pte = pte_mkyoung(_dst_pte); + + set_huge_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); + + (void)huge_ptep_set_access_flags(dst_vma, dst_addr, dst_pte, _dst_pte, + dst_vma->vm_flags & VM_WRITE); + hugetlb_count_add(pages_per_huge_page(h), dst_mm); + + /* No need to invalidate - it was non-present before */ + update_mmu_cache(dst_vma, dst_addr, dst_pte); + + spin_unlock(ptl); + ret = 0; +out: + return ret; +out_release_unlock: + spin_unlock(ptl); + put_page(page); + goto out; +} + long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, struct page **pages, struct vm_area_struct **vmas, unsigned long *position, unsigned long *nr_pages, -- 2.20.1