Btrfs: fix oops on page->mapping->host during writepage

[uclinux-h8/linux.git] / fs / btrfs / extent_io.c

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 5d66cb2..05a1c42 100644 (file)
--- 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;
 }