diff options
Diffstat (limited to 'mm/gup.c')
| -rw-r--r-- | mm/gup.c | 42 |
1 files changed, 29 insertions, 13 deletions
diff --git a/mm/gup.c b/mm/gup.c index 541904a7c60fd..1020c7f8f5ee5 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -212,53 +212,69 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, unsigned long address, pud_t *pudp, unsigned int flags, unsigned int *page_mask) { - pmd_t *pmd; + pmd_t *pmd, pmdval; spinlock_t *ptl; struct page *page; struct mm_struct *mm = vma->vm_mm; pmd = pmd_offset(pudp, address); - if (pmd_none(*pmd)) + /* + * The READ_ONCE() will stabilize the pmdval in a register or + * on the stack so that it will stop changing under the code. + */ + pmdval = READ_ONCE(*pmd); + if (pmd_none(pmdval)) return no_page_table(vma, flags); - if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) { + if (pmd_huge(pmdval) && vma->vm_flags & VM_HUGETLB) { page = follow_huge_pmd(mm, address, pmd, flags); if (page) return page; return no_page_table(vma, flags); } - if (is_hugepd(__hugepd(pmd_val(*pmd)))) { + if (is_hugepd(__hugepd(pmd_val(pmdval)))) { page = follow_huge_pd(vma, address, - __hugepd(pmd_val(*pmd)), flags, + __hugepd(pmd_val(pmdval)), flags, PMD_SHIFT); if (page) return page; return no_page_table(vma, flags); } retry: - if (!pmd_present(*pmd)) { + if (!pmd_present(pmdval)) { if (likely(!(flags & FOLL_MIGRATION))) return no_page_table(vma, flags); VM_BUG_ON(thp_migration_supported() && - !is_pmd_migration_entry(*pmd)); - if (is_pmd_migration_entry(*pmd)) + !is_pmd_migration_entry(pmdval)); + if (is_pmd_migration_entry(pmdval)) pmd_migration_entry_wait(mm, pmd); + pmdval = READ_ONCE(*pmd); + /* + * MADV_DONTNEED may convert the pmd to null because + * mmap_sem is held in read mode + */ + if (pmd_none(pmdval)) + return no_page_table(vma, flags); goto retry; } - if (pmd_devmap(*pmd)) { + if (pmd_devmap(pmdval)) { ptl = pmd_lock(mm, pmd); page = follow_devmap_pmd(vma, address, pmd, flags); spin_unlock(ptl); if (page) return page; } - if (likely(!pmd_trans_huge(*pmd))) + if (likely(!pmd_trans_huge(pmdval))) return follow_page_pte(vma, address, pmd, flags); - if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) + if ((flags & FOLL_NUMA) && pmd_protnone(pmdval)) return no_page_table(vma, flags); retry_locked: ptl = pmd_lock(mm, pmd); + if (unlikely(pmd_none(*pmd))) { + spin_unlock(ptl); + return no_page_table(vma, flags); + } if (unlikely(!pmd_present(*pmd))) { spin_unlock(ptl); if (likely(!(flags & FOLL_MIGRATION))) @@ -1354,7 +1370,7 @@ static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages) } } -#ifdef __HAVE_ARCH_PTE_SPECIAL +#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) { @@ -1430,7 +1446,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, { return 0; } -#endif /* __HAVE_ARCH_PTE_SPECIAL */ +#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */ #if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE) static int __gup_device_huge(unsigned long pfn, unsigned long addr, |