1 files changed, 30 insertions, 21 deletions

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 638edabaff71..955f9d0e38aa 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -27,7 +27,8 @@
 #include <asm/tlbflush.h>
 
 static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
-                unsigned long addr, unsigned long end, pgprot_t newprot)
+                unsigned long addr, unsigned long end, pgprot_t newprot,
+                int dirty_accountable)
 {
         pte_t *pte, oldpte;
         spinlock_t *ptl;
@@ -42,7 +43,14 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
                          * bits by wiping the pte and then setting the new pte
                          * into place.
                          */
-                        ptent = pte_modify(ptep_get_and_clear(mm, addr, pte), newprot);
+                        ptent = ptep_get_and_clear(mm, addr, pte);
+                        ptent = pte_modify(ptent, newprot);
+                        /*
+                         * Avoid taking write faults for pages we know to be
+                         * dirty.
+                         */
+                        if (dirty_accountable && pte_dirty(ptent))
+                                ptent = pte_mkwrite(ptent);
                         set_pte_at(mm, addr, pte, ptent);
                         lazy_mmu_prot_update(ptent);
 #ifdef CONFIG_MIGRATION
@@ -66,7 +74,8 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
 }
 
 static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
-                unsigned long addr, unsigned long end, pgprot_t newprot)
+                unsigned long addr, unsigned long end, pgprot_t newprot,
+                int dirty_accountable)
 {
         pmd_t *pmd;
         unsigned long next;
@@ -76,12 +85,13 @@ static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
                 next = pmd_addr_end(addr, end);
                 if (pmd_none_or_clear_bad(pmd))
                         continue;
-                change_pte_range(mm, pmd, addr, next, newprot);
+                change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable);
         } while (pmd++, addr = next, addr != end);
 }
 
 static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
-                unsigned long addr, unsigned long end, pgprot_t newprot)
+                unsigned long addr, unsigned long end, pgprot_t newprot,
+                int dirty_accountable)
 {
         pud_t *pud;
         unsigned long next;
@@ -91,12 +101,13 @@ static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
                 next = pud_addr_end(addr, end);
                 if (pud_none_or_clear_bad(pud))
                         continue;
-                change_pmd_range(mm, pud, addr, next, newprot);
+                change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable);
         } while (pud++, addr = next, addr != end);
 }
 
 static void change_protection(struct vm_area_struct *vma,
-                unsigned long addr, unsigned long end, pgprot_t newprot)
+                unsigned long addr, unsigned long end, pgprot_t newprot,
+                int dirty_accountable)
 {
         struct mm_struct *mm = vma->vm_mm;
         pgd_t *pgd;
@@ -110,7 +121,7 @@ static void change_protection(struct vm_area_struct *vma,
                 next = pgd_addr_end(addr, end);
                 if (pgd_none_or_clear_bad(pgd))
                         continue;
-                change_pud_range(mm, pgd, addr, next, newprot);
+                change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable);
         } while (pgd++, addr = next, addr != end);
         flush_tlb_range(vma, start, end);
 }
@@ -123,10 +134,9 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
         unsigned long oldflags = vma->vm_flags;
         long nrpages = (end - start) >> PAGE_SHIFT;
         unsigned long charged = 0;
-        unsigned int mask;
-        pgprot_t newprot;
         pgoff_t pgoff;
         int error;
+        int dirty_accountable = 0;
 
         if (newflags == oldflags) {
                 *pprev = vma;
@@ -176,24 +186,23 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
         }
 
 success:
-        /* Don't make the VMA automatically writable if it's shared, but the
-         * backer wishes to know when pages are first written to */
-        mask = VM_READ|VM_WRITE|VM_EXEC|VM_SHARED;
-        if (vma->vm_ops && vma->vm_ops->page_mkwrite)
-                mask &= ~VM_SHARED;
-
-        newprot = protection_map[newflags & mask];
-
         /*
          * vm_flags and vm_page_prot are protected by the mmap_sem
          * held in write mode.
          */
         vma->vm_flags = newflags;
-        vma->vm_page_prot = newprot;
+        vma->vm_page_prot = protection_map[newflags &
+                (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
+        if (vma_wants_writenotify(vma)) {
+                vma->vm_page_prot = protection_map[newflags &
+                        (VM_READ|VM_WRITE|VM_EXEC)];
+                dirty_accountable = 1;
+        }
+
         if (is_vm_hugetlb_page(vma))
-                hugetlb_change_protection(vma, start, end, newprot);
+                hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
         else
-                change_protection(vma, start, end, newprot);
+                change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
         vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
         vm_stat_account(mm, newflags, vma->vm_file, nrpages);
         return 0;