1 files changed, 32 insertions, 8 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 5d66cb27e422..05a1c42e25bf 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2104,6 +2104,16 @@ int extent_read_full_page(struct extent_io_tree *tree, struct page *page,
         return ret;
 }
 
+static noinline void update_nr_written(struct page *page,
+                                      struct writeback_control *wbc,
+                                      unsigned long nr_written)
+{
+        wbc->nr_to_write -= nr_written;
+        if (wbc->range_cyclic || (wbc->nr_to_write > 0 &&
+            wbc->range_start == 0 && wbc->range_end == LLONG_MAX))
+                page->mapping->writeback_index = page->index + nr_written;
+}
+
 /*
  * the writepage semantics are similar to regular writepage.  extent
  * records are inserted to lock ranges in the tree, and as dirty areas
@@ -2173,6 +2183,12 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
         delalloc_end = 0;
         page_started = 0;
         if (!epd->extent_locked) {
+                /*
+                 * make sure the wbc mapping index is at least updated
+                 * to this page.
+                 */
+                update_nr_written(page, wbc, 0);
+
                 while (delalloc_end < page_end) {
                         nr_delalloc = find_lock_delalloc_range(inode, tree,
                                                        page,
@@ -2194,7 +2210,13 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
                  */
                 if (page_started) {
                         ret = 0;
-                        goto update_nr_written;
+                        /*
+                         * we've unlocked the page, so we can't update
+                         * the mapping's writeback index, just update
+                         * nr_to_write.
+                         */
+                        wbc->nr_to_write -= nr_written;
+                        goto done_unlocked;
                 }
         }
         lock_extent(tree, start, page_end, GFP_NOFS);
@@ -2207,13 +2229,18 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
                 if (ret == -EAGAIN) {
                         unlock_extent(tree, start, page_end, GFP_NOFS);
                         redirty_page_for_writepage(wbc, page);
+                        update_nr_written(page, wbc, nr_written);
                         unlock_page(page);
                         ret = 0;
-                        goto update_nr_written;
+                        goto done_unlocked;
                 }
         }
 
-        nr_written++;
+        /*
+         * we don't want to touch the inode after unlocking the page,
+         * so we update the mapping writeback index now
+         */
+        update_nr_written(page, wbc, nr_written + 1);
 
         end = page_end;
         if (test_range_bit(tree, start, page_end, EXTENT_DELALLOC, 0))
@@ -2345,11 +2372,8 @@ done:
                 unlock_extent(tree, unlock_start, page_end, GFP_NOFS);
         unlock_page(page);
 
-update_nr_written:
-        wbc->nr_to_write -= nr_written;
-        if (wbc->range_cyclic || (wbc->nr_to_write > 0 &&
-            wbc->range_start == 0 && wbc->range_end == LLONG_MAX))
-                page->mapping->writeback_index = page->index + nr_written;
+done_unlocked:
+
         return 0;
 }