2 files changed, 40 insertions, 13 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6eb7f48317f8..82d7024f0765 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -625,10 +625,16 @@ static inline int page_mapped(struct page *page)
  * Used to decide whether a process gets delivered SIGBUS or
  * just gets major/minor fault counters bumped up.
  */
-#define VM_FAULT_OOM    (-1)
-#define VM_FAULT_SIGBUS 0
-#define VM_FAULT_MINOR  1
-#define VM_FAULT_MAJOR  2
+#define VM_FAULT_OOM    0x00
+#define VM_FAULT_SIGBUS 0x01
+#define VM_FAULT_MINOR  0x02
+#define VM_FAULT_MAJOR  0x03
+
+/* 
+ * Special case for get_user_pages.
+ * Must be in a distinct bit from the above VM_FAULT_ flags.
+ */
+#define VM_FAULT_WRITE  0x10
 
 #define offset_in_page(p)       ((unsigned long)(p) & ~PAGE_MASK)
 
@@ -704,7 +710,13 @@ extern pte_t *FASTCALL(pte_alloc_kernel(struct mm_struct *mm, pmd_t *pmd, unsign
 extern pte_t *FASTCALL(pte_alloc_map(struct mm_struct *mm, pmd_t *pmd, unsigned long address));
 extern int install_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, struct page *page, pgprot_t prot);
 extern int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, unsigned long pgoff, pgprot_t prot);
-extern int handle_mm_fault(struct mm_struct *mm,struct vm_area_struct *vma, unsigned long address, int write_access);
+extern int __handle_mm_fault(struct mm_struct *mm,struct vm_area_struct *vma, unsigned long address, int write_access);
+
+static inline int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int write_access)
+{
+        return __handle_mm_fault(mm, vma, address, write_access) & (~VM_FAULT_WRITE);
+}
+
 extern int make_pages_present(unsigned long addr, unsigned long end);
 extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write);
 void install_arg_page(struct vm_area_struct *, struct page *, unsigned long);
diff --git a/mm/memory.c b/mm/memory.c
index 2405289dfdf8..81d7117aa58b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -811,15 +811,18 @@ static struct page *__follow_page(struct mm_struct *mm, unsigned long address,
         pte = *ptep;
         pte_unmap(ptep);
         if (pte_present(pte)) {
-                if (write && !pte_dirty(pte))
+                if (write && !pte_write(pte))
                         goto out;
                 if (read && !pte_read(pte))
                         goto out;
                 pfn = pte_pfn(pte);
                 if (pfn_valid(pfn)) {
                         page = pfn_to_page(pfn);
-                        if (accessed)
+                        if (accessed) {
+                                if (write && !pte_dirty(pte) &&!PageDirty(page))
+                                        set_page_dirty(page);
                                 mark_page_accessed(page);
+                        }
                         return page;
                 }
         }
@@ -941,10 +944,11 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                 }
                 spin_lock(&mm->page_table_lock);
                 do {
+                        int write_access = write;
                         struct page *page;
 
                         cond_resched_lock(&mm->page_table_lock);
-                        while (!(page = follow_page(mm, start, write))) {
+                        while (!(page = follow_page(mm, start, write_access))) {
                                 /*
                                  * Shortcut for anonymous pages. We don't want
                                  * to force the creation of pages tables for
@@ -957,7 +961,16 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                         break;
                                 }
                                 spin_unlock(&mm->page_table_lock);
-                                switch (handle_mm_fault(mm,vma,start,write)) {
+                                switch (__handle_mm_fault(mm, vma, start,
+                                                        write_access)) {
+                                case VM_FAULT_WRITE:
+                                        /*
+                                         * do_wp_page has broken COW when
+                                         * necessary, even if maybe_mkwrite
+                                         * decided not to set pte_write
+                                         */
+                                        write_access = 0;
+                                        /* FALLTHRU */
                                 case VM_FAULT_MINOR:
                                         tsk->min_flt++;
                                         break;
@@ -1220,6 +1233,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
         struct page *old_page, *new_page;
         unsigned long pfn = pte_pfn(pte);
         pte_t entry;
+        int ret;
 
         if (unlikely(!pfn_valid(pfn))) {
                 /*
@@ -1247,7 +1261,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
                         lazy_mmu_prot_update(entry);
                         pte_unmap(page_table);
                         spin_unlock(&mm->page_table_lock);
-                        return VM_FAULT_MINOR;
+                        return VM_FAULT_MINOR|VM_FAULT_WRITE;
                 }
         }
         pte_unmap(page_table);
@@ -1274,6 +1288,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
         /*
          * Re-check the pte - we dropped the lock
          */
+        ret = VM_FAULT_MINOR;
         spin_lock(&mm->page_table_lock);
         page_table = pte_offset_map(pmd, address);
         if (likely(pte_same(*page_table, pte))) {
@@ -1290,12 +1305,13 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
 
                 /* Free the old page.. */
                 new_page = old_page;
+                ret |= VM_FAULT_WRITE;
         }
         pte_unmap(page_table);
         page_cache_release(new_page);
         page_cache_release(old_page);
         spin_unlock(&mm->page_table_lock);
-        return VM_FAULT_MINOR;
+        return ret;
 
 no_new_page:
         page_cache_release(old_page);
@@ -1987,7 +2003,6 @@ static inline int handle_pte_fault(struct mm_struct *mm,
         if (write_access) {
                 if (!pte_write(entry))
                         return do_wp_page(mm, vma, address, pte, pmd, entry);
-
                 entry = pte_mkdirty(entry);
         }
         entry = pte_mkyoung(entry);
@@ -2002,7 +2017,7 @@ static inline int handle_pte_fault(struct mm_struct *mm,
 /*
  * By the time we get here, we already hold the mm semaphore
  */
-int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
+int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
                 unsigned long address, int write_access)
 {
         pgd_t *pgd;