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;