diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index c683aaa925fa6793c6799318ff35ed4fad071a44..b9f9f815ed097dd93dad83dcc26c8b06735c837a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -81,6 +81,10 @@ struct btrfs_ordered_sum;
 #define BTRFS_TREE_LOG_OBJECTID -6ULL
 #define BTRFS_TREE_LOG_FIXUP_OBJECTID -7ULL
 
+/* for space balancing */
+#define BTRFS_TREE_RELOC_OBJECTID -8ULL
+#define BTRFS_DATA_RELOC_TREE_OBJECTID -9ULL
+
 /* dummy objectid represents multiple objectids */
 #define BTRFS_MULTIPLE_OBJECTIDS -255ULL
 
@@ -539,6 +543,12 @@ struct btrfs_block_group_cache {
 	struct list_head list;
 };
 
+struct btrfs_leaf_ref_tree {
+	struct rb_root root;
+	struct list_head list;
+	spinlock_t lock;
+};
+
 struct btrfs_device;
 struct btrfs_fs_devices;
 struct btrfs_fs_info {
@@ -637,6 +647,8 @@ struct btrfs_fs_info {
 	struct task_struct *cleaner_kthread;
 	int thread_pool_size;
 
+	struct btrfs_leaf_ref_tree shared_ref_tree;
+
 	struct kobject super_kobj;
 	struct completion kobj_unregister;
 	int do_barriers;
@@ -670,13 +682,6 @@ struct btrfs_fs_info {
 	void *bdev_holder;
 };
 
-struct btrfs_leaf_ref_tree {
-	struct rb_root root;
-	struct btrfs_leaf_ref *last;
-	struct list_head list;
-	spinlock_t lock;
-};
-
 /*
  * in ram representation of the tree.  extent_root is used for all allocations
  * and for the extent tree extent_root root.
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 71e81f3a765b8c53ce901123465551d3d8ab1e99..8969fee23318c0a2fb4043dce54d7f3eacf01a1a 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1406,6 +1406,8 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 			     fs_info->btree_inode->i_mapping, GFP_NOFS);
 	fs_info->do_barriers = 1;
 
+	btrfs_leaf_ref_tree_init(&fs_info->shared_ref_tree);
+
 	BTRFS_I(fs_info->btree_inode)->root = tree_root;
 	memset(&BTRFS_I(fs_info->btree_inode)->location, 0,
 	       sizeof(struct btrfs_key));
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3e2f969de42d9883635b0bdaea891ac48d3627a6..9ab099bc01a41f0066a28616dc662ffdc0b47043 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1091,16 +1091,26 @@ int btrfs_cross_ref_exists(struct btrfs_trans_handle *trans,
 int btrfs_cache_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 		    struct extent_buffer *buf, u32 nr_extents)
 {
-	u32 nritems;
 	struct btrfs_key key;
 	struct btrfs_file_extent_item *fi;
+	u64 root_gen;
+	u32 nritems;
 	int i;
 	int level;
 	int ret = 0;
+	int shared = 0;
 
 	if (!root->ref_cows)
 		return 0;
 
+	if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
+		shared = 0;
+		root_gen = root->root_key.offset;
+	} else {
+		shared = 1;
+		root_gen = trans->transid - 1;
+	}
+
 	level = btrfs_header_level(buf);
 	nritems = btrfs_header_nritems(buf);
 
@@ -1114,7 +1124,7 @@ int btrfs_cache_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 			goto out;
 		}
 
-		ref->root_gen = root->root_key.offset;
+		ref->root_gen = root_gen;
 		ref->bytenr = buf->start;
 		ref->owner = btrfs_header_owner(buf);
 		ref->generation = btrfs_header_generation(buf);
@@ -1143,8 +1153,7 @@ int btrfs_cache_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 			info++;
 		}
 
-		BUG_ON(!root->ref_tree);
-		ret = btrfs_add_leaf_ref(root, ref);
+		ret = btrfs_add_leaf_ref(root, ref, shared);
 		WARN_ON(ret);
 		btrfs_free_leaf_ref(root, ref);
 	}
diff --git a/fs/btrfs/ref-cache.c b/fs/btrfs/ref-cache.c
index 272b9890c9826d07a0564e7fe0d7c27bb402b81e..c5809988c875bf003f3d60c7a81ca8007b8b4572 100644
--- a/fs/btrfs/ref-cache.c
+++ b/fs/btrfs/ref-cache.c
@@ -78,7 +78,6 @@ static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
 	}
 
 	entry = rb_entry(node, struct btrfs_leaf_ref, rb_node);
-	entry->in_tree = 1;
 	rb_link_node(node, parent, p);
 	rb_insert_color(node, root);
 	return NULL;
@@ -103,23 +102,29 @@ static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
 	return NULL;
 }
 
-int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen)
+int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
+			   int shared)
 {
 	struct btrfs_leaf_ref *ref = NULL;
 	struct btrfs_leaf_ref_tree *tree = root->ref_tree;
 
+	if (shared)
+		tree = &root->fs_info->shared_ref_tree;
 	if (!tree)
 		return 0;
 
 	spin_lock(&tree->lock);
 	while(!list_empty(&tree->list)) {
 		ref = list_entry(tree->list.next, struct btrfs_leaf_ref, list);
-		BUG_ON(!ref->in_tree);
+		BUG_ON(ref->tree != tree);
 		if (ref->root_gen > max_root_gen)
 			break;
+		if (!xchg(&ref->in_tree, 0)) {
+			cond_resched_lock(&tree->lock);
+			continue;
+		}
 
 		rb_erase(&ref->rb_node, &tree->root);
-		ref->in_tree = 0;
 		list_del_init(&ref->list);
 
 		spin_unlock(&tree->lock);
@@ -137,32 +142,43 @@ struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
 	struct rb_node *rb;
 	struct btrfs_leaf_ref *ref = NULL;
 	struct btrfs_leaf_ref_tree *tree = root->ref_tree;
-
-	if (!tree)
-		return NULL;
-
-	spin_lock(&tree->lock);
-	rb = tree_search(&tree->root, bytenr);
-	if (rb)
-		ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
-	if (ref)
-		atomic_inc(&ref->usage);
-	spin_unlock(&tree->lock);
-	return ref;
+again:
+	if (tree) {
+		spin_lock(&tree->lock);
+		rb = tree_search(&tree->root, bytenr);
+		if (rb)
+			ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
+		if (ref)
+			atomic_inc(&ref->usage);
+		spin_unlock(&tree->lock);
+		if (ref)
+			return ref;
+	}
+	if (tree != &root->fs_info->shared_ref_tree) {
+		tree = &root->fs_info->shared_ref_tree;
+		goto again;
+	}
+	return NULL;
 }
 
-int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
+int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
+		       int shared)
 {
 	int ret = 0;
 	struct rb_node *rb;
 	struct btrfs_leaf_ref_tree *tree = root->ref_tree;
 
+	if (shared)
+		tree = &root->fs_info->shared_ref_tree;
+
 	spin_lock(&tree->lock);
 	rb = tree_insert(&tree->root, ref->bytenr, &ref->rb_node);
 	if (rb) {
 		ret = -EEXIST;
 	} else {
 		atomic_inc(&ref->usage);
+		ref->tree = tree;
+		ref->in_tree = 1;
 		list_add_tail(&ref->list, &tree->list);
 	}
 	spin_unlock(&tree->lock);
@@ -171,13 +187,15 @@ int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
 
 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
 {
-	struct btrfs_leaf_ref_tree *tree = root->ref_tree;
+	struct btrfs_leaf_ref_tree *tree;
+
+	if (!xchg(&ref->in_tree, 0))
+		return 0;
 
-	BUG_ON(!ref->in_tree);
+	tree = ref->tree;
 	spin_lock(&tree->lock);
 
 	rb_erase(&ref->rb_node, &tree->root);
-	ref->in_tree = 0;
 	list_del_init(&ref->list);
 
 	spin_unlock(&tree->lock);
diff --git a/fs/btrfs/ref-cache.h b/fs/btrfs/ref-cache.h
index c361b321c0c32289b2557c395354587c6f7656ef..617564787f521f9f6e8152d90a8c24a0c45285a3 100644
--- a/fs/btrfs/ref-cache.h
+++ b/fs/btrfs/ref-cache.h
@@ -27,6 +27,7 @@ struct btrfs_extent_info {
 
 struct btrfs_leaf_ref {
 	struct rb_node rb_node;
+	struct btrfs_leaf_ref_tree *tree;
 	int in_tree;
 	atomic_t usage;
 
@@ -64,8 +65,10 @@ struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
 void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
 struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
 					     u64 bytenr);
-int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
-int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen);
+int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
+		       int shared);
+int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
+			   int shared);
 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
 
 #endif
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 151b00d52593533a095ca14c333e71353d3b7469..656baefa5255033f27f26d620f8a0ba24f8e1b8a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -650,7 +650,7 @@ static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
 		ret = btrfs_end_transaction(trans, tree_root);
 		BUG_ON(ret);
 
-		ret = btrfs_remove_leaf_refs(root, max_useless);
+		ret = btrfs_remove_leaf_refs(root, max_useless, 0);
 		BUG_ON(ret);
 
 		free_extent_buffer(dirty->root->node);