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/disk-io.c b/fs/btrfs/disk-io.c
index 2b59201b955c..0427183e3e05 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -901,7 +901,7 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
         root->highest_objectid = 0;
         root->name = NULL;
         root->in_sysfs = 0;
-        root->inode_tree.rb_node = NULL;
+        root->inode_tree = RB_ROOT;
 
         INIT_LIST_HEAD(&root->dirty_list);
         INIT_LIST_HEAD(&root->orphan_list);
@@ -1673,7 +1673,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         insert_inode_hash(fs_info->btree_inode);
 
         spin_lock_init(&fs_info->block_group_cache_lock);
-        fs_info->block_group_cache_tree.rb_node = NULL;
+        fs_info->block_group_cache_tree = RB_ROOT;
 
         extent_io_tree_init(&fs_info->freed_extents[0],
                              fs_info->btree_inode->i_mapping, GFP_NOFS);