btrfs: remove pointless in_tree field from struct btrfs_delayed_ref_node

The 'in_tree' field is really not needed in struct btrfs_delayed_ref_node,
as we can check whether a reference is in the tree or not simply by
checking its red black tree node member with RB_EMPTY_NODE(), as when we
remove it from the tree we always call RB_CLEAR_NODE(). So remove that
field and use RB_EMPTY_NODE().
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/delayed-ref.c

@@ -407,7 +407,6 @@ static inline void drop_delayed_ref(struct btrfs_delayed_ref_root *delayed_refs,
 	RB_CLEAR_NODE(&ref->ref_node);
 	if (!list_empty(&ref->add_list))
 		list_del(&ref->add_list);
-	ref->in_tree = 0;
 	btrfs_put_delayed_ref(ref);
 	atomic_dec(&delayed_refs->num_entries);
 }
@@ -853,7 +852,6 @@ static void init_delayed_ref_common(struct btrfs_fs_info *fs_info,
 	ref->num_bytes = num_bytes;
 	ref->ref_mod = 1;
 	ref->action = action;
-	ref->in_tree = 1;
 	ref->seq = seq;
 	ref->type = ref_type;
 	RB_CLEAR_NODE(&ref->ref_node);

fs/btrfs/delayed-ref.h

@@ -48,7 +48,6 @@ struct btrfs_delayed_ref_node {
 
 	unsigned int action:8;
 	unsigned int type:8;
-	unsigned int in_tree:1;
 };
 
 struct btrfs_delayed_extent_op {
@@ -341,7 +340,7 @@ static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
 {
 	WARN_ON(refcount_read(&ref->refs) == 0);
 	if (refcount_dec_and_test(&ref->refs)) {
-		WARN_ON(ref->in_tree);
+		WARN_ON(!RB_EMPTY_NODE(&ref->ref_node));
 		switch (ref->type) {
 		case BTRFS_TREE_BLOCK_REF_KEY:
 		case BTRFS_SHARED_BLOCK_REF_KEY:

fs/btrfs/disk-io.c

@@ -4602,7 +4602,6 @@ static int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
 		while ((n = rb_first_cached(&head->ref_tree)) != NULL) {
 			ref = rb_entry(n, struct btrfs_delayed_ref_node,
 				       ref_node);
-			ref->in_tree = 0;
 			rb_erase_cached(&ref->ref_node, &head->ref_tree);
 			RB_CLEAR_NODE(&ref->ref_node);
 			if (!list_empty(&ref->add_list))

fs/btrfs/extent-tree.c

@@ -1913,7 +1913,6 @@ static int btrfs_run_delayed_refs_for_head(struct btrfs_trans_handle *trans,
 			return -EAGAIN;
 		}
 
-		ref->in_tree = 0;
 		rb_erase_cached(&ref->ref_node, &locked_ref->ref_tree);
 		RB_CLEAR_NODE(&ref->ref_node);
 		if (!list_empty(&ref->add_list))