Btrfs: Full back reference support

This patch makes the back reference system to explicit record the
location of parent node for all types of extents. The location of
parent node is placed into the offset field of backref key. Every
time a tree block is balanced, the back references for the affected
lower level extents are updated.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 8624f3e88036..58ad25838a41 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2201,9 +2201,10 @@ retry:
         }
         if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
                 mapping->writeback_index = index;
-
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,26)
         if (wbc->range_cont)
                 wbc->range_start = index << PAGE_CACHE_SHIFT;
+#endif
         return ret;
 }
 EXPORT_SYMBOL(extent_write_cache_pages);