Btrfs: use RB_ROOT to intialize rb_trees instead of setting rb_node to NULL

btrfs inialize rb trees in quite a number of places by settin rb_node =
NULL;  The problem with this is that 17d9ddc72fb8bba0d4f678 in the
linux-next tree adds a new field to that struct which needs to be NULL for
the new rbtree library code to work properly.  This patch uses RB_ROOT as
the intializer so all of the relevant fields will be NULL'd.  Without the
patch I get a panic.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index b177ed319612..7073cbb1b2d4 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -104,8 +104,8 @@ void extent_io_exit(void)
 void extent_io_tree_init(struct extent_io_tree *tree,
                           struct address_space *mapping, gfp_t mask)
 {
-        tree->state.rb_node = NULL;
-        tree->buffer.rb_node = NULL;
+        tree->state = RB_ROOT;
+        tree->buffer = RB_ROOT;
         tree->ops = NULL;
         tree->dirty_bytes = 0;
         spin_lock_init(&tree->lock);