1 files changed, 17 insertions, 31 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 0e9b32610655..988d3099a25d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2005,7 +2005,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
         pte_t entry;
         int ret = 0;
         int page_mkwrite = 0;
-        struct page *dirty_page = NULL;
+        bool dirty_shared = false;
         unsigned long mmun_start = 0;   /* For mmu_notifiers */
         unsigned long mmun_end = 0;     /* For mmu_notifiers */
         struct mem_cgroup *memcg;
@@ -2056,6 +2056,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 unlock_page(old_page);
         } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
                                         (VM_WRITE|VM_SHARED))) {
+                page_cache_get(old_page);
                 /*
                  * Only catch write-faults on shared writable pages,
                  * read-only shared pages can get COWed by
@@ -2063,7 +2064,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
                  */
                 if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
                         int tmp;
-                        page_cache_get(old_page);
+
                         pte_unmap_unlock(page_table, ptl);
                         tmp = do_page_mkwrite(vma, old_page, address);
                         if (unlikely(!tmp || (tmp &
@@ -2083,11 +2084,10 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
                                 unlock_page(old_page);
                                 goto unlock;
                         }
-
                         page_mkwrite = 1;
                 }
-                dirty_page = old_page;
-                get_page(dirty_page);
+
+                dirty_shared = true;
 
 reuse:
                 /*
@@ -2106,43 +2106,29 @@ reuse:
                 pte_unmap_unlock(page_table, ptl);
                 ret |= VM_FAULT_WRITE;
 
-                if (!dirty_page)
-                        return ret;
-
-                if (!page_mkwrite) {
+                if (dirty_shared) {
                         struct address_space *mapping;
                         int dirtied;
 
-                        lock_page(dirty_page);
-                        dirtied = set_page_dirty(dirty_page);
-                        VM_BUG_ON_PAGE(PageAnon(dirty_page), dirty_page);
-                        mapping = dirty_page->mapping;
-                        unlock_page(dirty_page);
+                        if (!page_mkwrite)
+                                lock_page(old_page);
 
-                        if (dirtied && mapping) {
-                                /*
-                                 * Some device drivers do not set page.mapping
-                                 * but still dirty their pages
-                                 */
-                                balance_dirty_pages_ratelimited(mapping);
-                        }
+                        dirtied = set_page_dirty(old_page);
+                        VM_BUG_ON_PAGE(PageAnon(old_page), old_page);
+                        mapping = old_page->mapping;
+                        unlock_page(old_page);
+                        page_cache_release(old_page);
 
-                        file_update_time(vma->vm_file);
-                }
-                put_page(dirty_page);
-                if (page_mkwrite) {
-                        struct address_space *mapping = dirty_page->mapping;
-
-                        set_page_dirty(dirty_page);
-                        unlock_page(dirty_page);
-                        page_cache_release(dirty_page);
-                        if (mapping)    {
+                        if ((dirtied || page_mkwrite) && mapping) {
                                 /*
                                  * Some device drivers do not set page.mapping
                                  * but still dirty their pages
                                  */
                                 balance_dirty_pages_ratelimited(mapping);
                         }
+
+                        if (!page_mkwrite)
+                                file_update_time(vma->vm_file);
                 }
 
                 return ret;