1 files changed, 21 insertions, 9 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 9d6aefa937c4..f3a384ed700c 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1663,6 +1663,13 @@ void set_page_extent_mapped(struct page *page)
         }
 }
 
+void set_page_extent_head(struct page *page, unsigned long len)
+{
+        WARN_ON(page->private && page->private == EXTENT_PAGE_PRIVATE &&
+                PageDirty(page));
+        set_page_private(page, EXTENT_PAGE_PRIVATE_FIRST_PAGE | len << 2);
+}
+
 /*
  * basic readpage implementation.  Locked extent state structs are inserted
  * into the tree that are removed when the IO is done (by the end_io
@@ -2490,8 +2497,7 @@ struct extent_buffer *alloc_extent_buffer(struct extent_map_tree *tree,
                 mark_page_accessed(page0);
                 set_page_extent_mapped(page0);
                 WARN_ON(!PageUptodate(page0));
-                set_page_private(page0, EXTENT_PAGE_PRIVATE_FIRST_PAGE |
-                                 len << 2);
+                set_page_extent_head(page0, len);
         } else {
                 i = 0;
         }
@@ -2505,8 +2511,7 @@ struct extent_buffer *alloc_extent_buffer(struct extent_map_tree *tree,
                 mark_page_accessed(p);
                 if (i == 0) {
                         eb->first_page = p;
-                        set_page_private(p, EXTENT_PAGE_PRIVATE_FIRST_PAGE |
-                                         len << 2);
+                        set_page_extent_head(p, len);
                 } else {
                         set_page_private(p, EXTENT_PAGE_PRIVATE);
                 }
@@ -2569,8 +2574,7 @@ struct extent_buffer *find_extent_buffer(struct extent_map_tree *tree,
 
                 if (i == 0) {
                         eb->first_page = p;
-                        set_page_private(p, EXTENT_PAGE_PRIVATE_FIRST_PAGE |
-                                         len << 2);
+                        set_page_extent_head(p, len);
                 } else {
                         set_page_private(p, EXTENT_PAGE_PRIVATE);
                 }
@@ -2643,6 +2647,11 @@ int clear_extent_buffer_dirty(struct extent_map_tree *tree,
         for (i = 0; i < num_pages; i++) {
                 page = extent_buffer_page(eb, i);
                 lock_page(page);
+                if (i == 0)
+                        set_page_extent_head(page, eb->len);
+                else
+                        set_page_private(page, EXTENT_PAGE_PRIVATE);
+
                 /*
                  * if we're on the last page or the first page and the
                  * block isn't aligned on a page boundary, do extra checks
@@ -2697,9 +2706,12 @@ int set_extent_buffer_dirty(struct extent_map_tree *tree,
                  */
                 if (i == 0) {
                         lock_page(page);
-                        set_page_private(page,
-                                         EXTENT_PAGE_PRIVATE_FIRST_PAGE |
-                                         eb->len << 2);
+                        set_page_extent_head(page, eb->len);
+                } else if (PagePrivate(page) &&
+                           page->private != EXTENT_PAGE_PRIVATE) {
+                        lock_page(page);
+                        set_page_extent_mapped(page);
+                        unlock_page(page);
                 }
                 __set_page_dirty_nobuffers(extent_buffer_page(eb, i));
                 if (i == 0)