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>

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);

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);

fs/btrfs/extent_map.c

@@ -35,7 +35,7 @@ void extent_map_exit(void)
  */
 void extent_map_tree_init(struct extent_map_tree *tree, gfp_t mask)
 {
-	tree->map.rb_node = NULL;
+	tree->map = RB_ROOT;
 	rwlock_init(&tree->lock);
 }
 

fs/btrfs/free-space-cache.c

@@ -870,7 +870,7 @@ __btrfs_return_cluster_to_free_space(
 		tree_insert_offset(&block_group->free_space_offset,
 				   entry->offset, &entry->offset_index, 0);
 	}
-	cluster->root.rb_node = NULL;
+	cluster->root = RB_ROOT;
 
 out:
 	spin_unlock(&cluster->lock);
@@ -1355,7 +1355,7 @@ void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
 {
 	spin_lock_init(&cluster->lock);
 	spin_lock_init(&cluster->refill_lock);
-	cluster->root.rb_node = NULL;
+	cluster->root = RB_ROOT;
 	cluster->max_size = 0;
 	cluster->points_to_bitmap = false;
 	INIT_LIST_HEAD(&cluster->block_group_list);

fs/btrfs/ordered-data.h

@@ -129,7 +129,7 @@ static inline void
 btrfs_ordered_inode_tree_init(struct btrfs_ordered_inode_tree *t)
 {
 	mutex_init(&t->mutex);
-	t->tree.rb_node = NULL;
+	t->tree = RB_ROOT;
 	t->last = NULL;
 }
 

fs/btrfs/ref-cache.h

@@ -52,7 +52,7 @@ static inline size_t btrfs_leaf_ref_size(int nr_extents)
 
 static inline void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree)
 {
-	tree->root.rb_node = NULL;
+	tree->root = RB_ROOT;
 	INIT_LIST_HEAD(&tree->list);
 	spin_lock_init(&tree->lock);
 }

fs/btrfs/relocation.c

@@ -170,14 +170,14 @@ struct async_merge {
 
 static void mapping_tree_init(struct mapping_tree *tree)
 {
-	tree->rb_root.rb_node = NULL;
+	tree->rb_root = RB_ROOT;
 	spin_lock_init(&tree->lock);
 }
 
 static void backref_cache_init(struct backref_cache *cache)
 {
 	int i;
-	cache->rb_root.rb_node = NULL;
+	cache->rb_root = RB_ROOT;
 	for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 		INIT_LIST_HEAD(&cache->pending[i]);
 	spin_lock_init(&cache->lock);

fs/btrfs/transaction.c

@@ -69,7 +69,7 @@ static noinline int join_transaction(struct btrfs_root *root)
 		cur_trans->commit_done = 0;
 		cur_trans->start_time = get_seconds();
 
-		cur_trans->delayed_refs.root.rb_node = NULL;
+		cur_trans->delayed_refs.root = RB_ROOT;
 		cur_trans->delayed_refs.num_entries = 0;
 		cur_trans->delayed_refs.num_heads_ready = 0;
 		cur_trans->delayed_refs.num_heads = 0;