mlock: fix mlock count can not decrease in race condition

[firefly-linux-kernel-4.4.55.git] / mm / huge_memory.c

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 62fe06bb7d04bacccc8c2213a6a65134fa274010..47b46966382223f5b91b09c179ea0d9981565650 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1269,6 +1269,16 @@ out_unlock:
        return ret;
 }
 
+/*
+ * FOLL_FORCE can write to even unwritable pmd's, but only
+ * after we've gone through a COW cycle and they are dirty.
+ */
+static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
+{
+       return pmd_write(pmd) ||
+              ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
+}
+
 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
                                   unsigned long addr,
                                   pmd_t *pmd,
@@ -1279,7 +1289,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
 
        assert_spin_locked(pmd_lockptr(mm, pmd));
 
-       if (flags & FOLL_WRITE && !pmd_write(*pmd))
+       if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
                goto out;
 
        /* Avoid dumping huge zero page */
@@ -2134,10 +2144,9 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
                 * page fault if needed.
                 */
                return 0;
-       if (vma->vm_ops)
+       if (vma->vm_ops || (vm_flags & VM_NO_THP))
                /* khugepaged not yet working on file or special mappings */
                return 0;
-       VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
        hend = vma->vm_end & HPAGE_PMD_MASK;
        if (hstart < hend)
@@ -2498,8 +2507,7 @@ static bool hugepage_vma_check(struct vm_area_struct *vma)
                return false;
        if (is_vma_temporary_stack(vma))
                return false;
-       VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
-       return true;
+       return !(vma->vm_flags & VM_NO_THP);
 }
 
 static void collapse_huge_page(struct mm_struct *mm,