diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 9ab099b..8043b9d 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1834,6 +1834,7 @@
 		u64 header_owner = btrfs_header_owner(buf);
 		u64 header_transid = btrfs_header_generation(buf);
 		if (header_owner != BTRFS_TREE_LOG_OBJECTID &&
+		    header_owner != BTRFS_TREE_RELOC_OBJECTID &&
 		    header_transid == trans->transid &&
 		    !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
 			clean_tree_block(NULL, root, buf);
@@ -2487,6 +2488,7 @@
 		return -ENOSPC;
 	}
 	btrfs_add_free_space(cache, start, len);
+	update_reserved_extents(root, start, len, 0);
 	maybe_unlock_mutex(root);
 	return 0;
 }
@@ -2947,6 +2949,10 @@
 		 */
 		if (*level == 1) {
 			ref = btrfs_lookup_leaf_ref(root, bytenr);
+			if (ref && ref->generation != ptr_gen) {
+				btrfs_free_leaf_ref(root, ref);
+				ref = NULL;
+			}
 			if (ref) {
 				ret = cache_drop_leaf_ref(trans, root, ref);
 				BUG_ON(ret);
@@ -3153,34 +3159,6 @@
 	return ret;
 }
 
-int btrfs_free_block_groups(struct btrfs_fs_info *info)
-{
-	struct btrfs_block_group_cache *block_group;
-	struct rb_node *n;
-
-	mutex_lock(&info->alloc_mutex);
-	spin_lock(&info->block_group_cache_lock);
-	while ((n = rb_last(&info->block_group_cache_tree)) != NULL) {
-		block_group = rb_entry(n, struct btrfs_block_group_cache,
-				       cache_node);
-
-		spin_unlock(&info->block_group_cache_lock);
-		btrfs_remove_free_space_cache(block_group);
-		spin_lock(&info->block_group_cache_lock);
-
-		rb_erase(&block_group->cache_node,
-			 &info->block_group_cache_tree);
-
-		spin_lock(&block_group->space_info->lock);
-		list_del(&block_group->list);
-		spin_unlock(&block_group->space_info->lock);
-		kfree(block_group);
-	}
-	spin_unlock(&info->block_group_cache_lock);
-	mutex_unlock(&info->alloc_mutex);
-	return 0;
-}
-
 static unsigned long calc_ra(unsigned long start, unsigned long last,
 			     unsigned long nr)
 {
@@ -3192,37 +3170,43 @@
 {
 	u64 page_start;
 	u64 page_end;
+	unsigned long first_index;
 	unsigned long last_index;
 	unsigned long i;
 	struct page *page;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	struct file_ra_state *ra;
-	unsigned long total_read = 0;
-	unsigned long ra_pages;
 	struct btrfs_ordered_extent *ordered;
-	struct btrfs_trans_handle *trans;
+	unsigned int total_read = 0;
+	unsigned int total_dirty = 0;
+	int ret = 0;
 
 	ra = kzalloc(sizeof(*ra), GFP_NOFS);
 
 	mutex_lock(&inode->i_mutex);
-	i = start >> PAGE_CACHE_SHIFT;
+	first_index = start >> PAGE_CACHE_SHIFT;
 	last_index = (start + len - 1) >> PAGE_CACHE_SHIFT;
 
-	ra_pages = BTRFS_I(inode)->root->fs_info->bdi.ra_pages;
+	/* make sure the dirty trick played by the caller work */
+	ret = invalidate_inode_pages2_range(inode->i_mapping,
+					    first_index, last_index);
+	if (ret)
+		goto out_unlock;
 
 	file_ra_state_init(ra, inode->i_mapping);
 
-	for (; i <= last_index; i++) {
-		if (total_read % ra_pages == 0) {
+	for (i = first_index ; i <= last_index; i++) {
+		if (total_read % ra->ra_pages == 0) {
 			btrfs_force_ra(inode->i_mapping, ra, NULL, i,
-				       calc_ra(i, last_index, ra_pages));
+				       calc_ra(i, last_index, ra->ra_pages));
 		}
 		total_read++;
 again:
 		if (((u64)i << PAGE_CACHE_SHIFT) > i_size_read(inode))
-			goto truncate_racing;
+			BUG_ON(1);
 		page = grab_cache_page(inode->i_mapping, i);
 		if (!page) {
+			ret = -ENOMEM;
 			goto out_unlock;
 		}
 		if (!PageUptodate(page)) {
@@ -3231,6 +3215,7 @@
 			if (!PageUptodate(page)) {
 				unlock_page(page);
 				page_cache_release(page);
+				ret = -EIO;
 				goto out_unlock;
 			}
 		}
@@ -3251,14 +3236,13 @@
 		}
 		set_page_extent_mapped(page);
 
-		/*
-		 * make sure page_mkwrite is called for this page if userland
-		 * wants to change it from mmap
-		 */
-		clear_page_dirty_for_io(page);
-
 		btrfs_set_extent_delalloc(inode, page_start, page_end);
+		if (i == first_index)
+			set_extent_bits(io_tree, page_start, page_end,
+					EXTENT_BOUNDARY, GFP_NOFS);
+
 		set_page_dirty(page);
+		total_dirty++;
 
 		unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
 		unlock_page(page);
@@ -3266,347 +3250,1457 @@
 	}
 
 out_unlock:
-	/* we have to start the IO in order to get the ordered extents
-	 * instantiated.  This allows the relocation to code to wait
-	 * for all the ordered extents to hit the disk.
-	 *
-	 * Otherwise, it would constantly loop over the same extents
-	 * because the old ones don't get deleted  until the IO is
-	 * started
-	 */
-	btrfs_fdatawrite_range(inode->i_mapping, start, start + len - 1,
-			       WB_SYNC_NONE);
 	kfree(ra);
-	trans = btrfs_start_transaction(BTRFS_I(inode)->root, 1);
-	if (trans) {
-		btrfs_end_transaction(trans, BTRFS_I(inode)->root);
-		mark_inode_dirty(inode);
-	}
 	mutex_unlock(&inode->i_mutex);
-	return 0;
-
-truncate_racing:
-	vmtruncate(inode, inode->i_size);
-	balance_dirty_pages_ratelimited_nr(inode->i_mapping,
-					   total_read);
-	goto out_unlock;
-}
-
-/*
- * The back references tell us which tree holds a ref on a block,
- * but it is possible for the tree root field in the reference to
- * reflect the original root before a snapshot was made.  In this
- * case we should search through all the children of a given root
- * to find potential holders of references on a block.
- *
- * Instead, we do something a little less fancy and just search
- * all the roots for a given key/block combination.
- */
-static int find_root_for_ref(struct btrfs_root *root,
-			     struct btrfs_path *path,
-			     struct btrfs_key *key0,
-			     int level,
-			     int file_key,
-			     struct btrfs_root **found_root,
-			     u64 bytenr)
-{
-	struct btrfs_key root_location;
-	struct btrfs_root *cur_root = *found_root;
-	struct btrfs_file_extent_item *file_extent;
-	u64 root_search_start = BTRFS_FS_TREE_OBJECTID;
-	u64 found_bytenr;
-	int ret;
-
-	root_location.offset = (u64)-1;
-	root_location.type = BTRFS_ROOT_ITEM_KEY;
-	path->lowest_level = level;
-	path->reada = 0;
-	while(1) {
-		ret = btrfs_search_slot(NULL, cur_root, key0, path, 0, 0);
-		found_bytenr = 0;
-		if (ret == 0 && file_key) {
-			struct extent_buffer *leaf = path->nodes[0];
-			file_extent = btrfs_item_ptr(leaf, path->slots[0],
-					     struct btrfs_file_extent_item);
-			if (btrfs_file_extent_type(leaf, file_extent) ==
-			    BTRFS_FILE_EXTENT_REG) {
-				found_bytenr =
-					btrfs_file_extent_disk_bytenr(leaf,
-							       file_extent);
-		       }
-		} else if (!file_key) {
-			if (path->nodes[level])
-				found_bytenr = path->nodes[level]->start;
-		}
-
-		btrfs_release_path(cur_root, path);
-
-		if (found_bytenr == bytenr) {
-			*found_root = cur_root;
-			ret = 0;
-			goto out;
-		}
-		ret = btrfs_search_root(root->fs_info->tree_root,
-					root_search_start, &root_search_start);
-		if (ret)
-			break;
-
-		root_location.objectid = root_search_start;
-		cur_root = btrfs_read_fs_root_no_name(root->fs_info,
-						      &root_location);
-		if (!cur_root) {
-			ret = 1;
-			break;
-		}
-	}
-out:
-	path->lowest_level = 0;
+	balance_dirty_pages_ratelimited_nr(inode->i_mapping, total_dirty);
 	return ret;
 }
 
-/*
- * note, this releases the path
- */
-static int noinline relocate_one_reference(struct btrfs_root *extent_root,
-				  struct btrfs_path *path,
-				  struct btrfs_key *extent_key,
-				  u64 *last_file_objectid,
-				  u64 *last_file_offset,
-				  u64 *last_file_root,
-				  u64 last_extent)
+static int noinline relocate_data_extent(struct inode *reloc_inode,
+					 struct btrfs_key *extent_key,
+					 u64 offset)
 {
-	struct inode *inode;
-	struct btrfs_root *found_root;
-	struct btrfs_key root_location;
-	struct btrfs_key found_key;
+	struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
+	struct extent_map_tree *em_tree = &BTRFS_I(reloc_inode)->extent_tree;
+	struct extent_map *em;
+
+	em = alloc_extent_map(GFP_NOFS);
+	BUG_ON(!em || IS_ERR(em));
+
+	em->start = extent_key->objectid - offset;
+	em->len = extent_key->offset;
+	em->block_start = extent_key->objectid;
+	em->bdev = root->fs_info->fs_devices->latest_bdev;
+	set_bit(EXTENT_FLAG_PINNED, &em->flags);
+
+	/* setup extent map to cheat btrfs_readpage */
+	mutex_lock(&BTRFS_I(reloc_inode)->extent_mutex);
+	while (1) {
+		int ret;
+		spin_lock(&em_tree->lock);
+		ret = add_extent_mapping(em_tree, em);
+		spin_unlock(&em_tree->lock);
+		if (ret != -EEXIST) {
+			free_extent_map(em);
+			break;
+		}
+		btrfs_drop_extent_cache(reloc_inode, em->start,
+					em->start + em->len - 1, 0);
+	}
+	mutex_unlock(&BTRFS_I(reloc_inode)->extent_mutex);
+
+	return relocate_inode_pages(reloc_inode, extent_key->objectid - offset,
+				    extent_key->offset);
+}
+
+struct btrfs_ref_path {
+	u64 extent_start;
+	u64 nodes[BTRFS_MAX_LEVEL];
+	u64 root_objectid;
+	u64 root_generation;
+	u64 owner_objectid;
+	u64 owner_offset;
+	u32 num_refs;
+	int lowest_level;
+	int current_level;
+};
+
+struct disk_extent {
+	u64 disk_bytenr;
+	u64 disk_num_bytes;
+	u64 offset;
+	u64 num_bytes;
+};
+
+static int is_cowonly_root(u64 root_objectid)
+{
+	if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
+	    root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
+	    root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
+	    root_objectid == BTRFS_DEV_TREE_OBJECTID ||
+	    root_objectid == BTRFS_TREE_LOG_OBJECTID)
+		return 1;
+	return 0;
+}
+
+static int noinline __next_ref_path(struct btrfs_trans_handle *trans,
+				    struct btrfs_root *extent_root,
+				    struct btrfs_ref_path *ref_path,
+				    int first_time)
+{
+	struct extent_buffer *leaf;
+	struct btrfs_path *path;
 	struct btrfs_extent_ref *ref;
-	u64 ref_root;
-	u64 ref_gen;
-	u64 ref_objectid;
-	u64 ref_offset;
-	int ret;
-	int level;
-
-	WARN_ON(!mutex_is_locked(&extent_root->fs_info->alloc_mutex));
-
-	ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
-			     struct btrfs_extent_ref);
-	ref_root = btrfs_ref_root(path->nodes[0], ref);
-	ref_gen = btrfs_ref_generation(path->nodes[0], ref);
-	ref_objectid = btrfs_ref_objectid(path->nodes[0], ref);
-	ref_offset = btrfs_ref_offset(path->nodes[0], ref);
-	btrfs_release_path(extent_root, path);
-
-	root_location.objectid = ref_root;
-	if (ref_gen == 0)
-		root_location.offset = 0;
-	else
-		root_location.offset = (u64)-1;
-	root_location.type = BTRFS_ROOT_ITEM_KEY;
-
-	found_root = btrfs_read_fs_root_no_name(extent_root->fs_info,
-						&root_location);
-	BUG_ON(!found_root);
-	mutex_unlock(&extent_root->fs_info->alloc_mutex);
-
-	if (ref_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
-		found_key.objectid = ref_objectid;
-		found_key.type = BTRFS_EXTENT_DATA_KEY;
-		found_key.offset = ref_offset;
-		level = 0;
-
-		if (last_extent == extent_key->objectid &&
-		    *last_file_objectid == ref_objectid &&
-		    *last_file_offset == ref_offset &&
-		    *last_file_root == ref_root)
-			goto out;
-
-		ret = find_root_for_ref(extent_root, path, &found_key,
-					level, 1, &found_root,
-					extent_key->objectid);
-
-		if (ret)
-			goto out;
-
-		if (last_extent == extent_key->objectid &&
-		    *last_file_objectid == ref_objectid &&
-		    *last_file_offset == ref_offset &&
-		    *last_file_root == ref_root)
-			goto out;
-
-		inode = btrfs_iget_locked(extent_root->fs_info->sb,
-					  ref_objectid, found_root);
-		if (inode->i_state & I_NEW) {
-			/* the inode and parent dir are two different roots */
-			BTRFS_I(inode)->root = found_root;
-			BTRFS_I(inode)->location.objectid = ref_objectid;
-			BTRFS_I(inode)->location.type = BTRFS_INODE_ITEM_KEY;
-			BTRFS_I(inode)->location.offset = 0;
-			btrfs_read_locked_inode(inode);
-			unlock_new_inode(inode);
-
-		}
-		/* this can happen if the reference is not against
-		 * the latest version of the tree root
-		 */
-		if (is_bad_inode(inode))
-			goto out;
-
-		*last_file_objectid = inode->i_ino;
-		*last_file_root = found_root->root_key.objectid;
-		*last_file_offset = ref_offset;
-
-		relocate_inode_pages(inode, ref_offset, extent_key->offset);
-		iput(inode);
-	} else {
-		struct btrfs_trans_handle *trans;
-		struct extent_buffer *eb;
-		int needs_lock = 0;
-
-		eb = read_tree_block(found_root, extent_key->objectid,
-				     extent_key->offset, 0);
-		btrfs_tree_lock(eb);
-		level = btrfs_header_level(eb);
-
-		if (level == 0)
-			btrfs_item_key_to_cpu(eb, &found_key, 0);
-		else
-			btrfs_node_key_to_cpu(eb, &found_key, 0);
-
-		btrfs_tree_unlock(eb);
-		free_extent_buffer(eb);
-
-		ret = find_root_for_ref(extent_root, path, &found_key,
-					level, 0, &found_root,
-					extent_key->objectid);
-
-		if (ret)
-			goto out;
-
-		/*
-		 * right here almost anything could happen to our key,
-		 * but that's ok.  The cow below will either relocate it
-		 * or someone else will have relocated it.  Either way,
-		 * it is in a different spot than it was before and
-		 * we're happy.
-		 */
-
-		trans = btrfs_start_transaction(found_root, 1);
-
-		if (found_root == extent_root->fs_info->extent_root ||
-		    found_root == extent_root->fs_info->chunk_root ||
-		    found_root == extent_root->fs_info->dev_root) {
-			needs_lock = 1;
-			mutex_lock(&extent_root->fs_info->alloc_mutex);
-		}
-
-		path->lowest_level = level;
-		path->reada = 2;
-		ret = btrfs_search_slot(trans, found_root, &found_key, path,
-					0, 1);
-		path->lowest_level = 0;
-		btrfs_release_path(found_root, path);
-
-		if (found_root == found_root->fs_info->extent_root)
-			btrfs_extent_post_op(trans, found_root);
-		if (needs_lock)
-			mutex_unlock(&extent_root->fs_info->alloc_mutex);
-
-		btrfs_end_transaction(trans, found_root);
-
-	}
-out:
-	mutex_lock(&extent_root->fs_info->alloc_mutex);
-	return 0;
-}
-
-static int noinline del_extent_zero(struct btrfs_root *extent_root,
-				    struct btrfs_path *path,
-				    struct btrfs_key *extent_key)
-{
-	int ret;
-	struct btrfs_trans_handle *trans;
-
-	trans = btrfs_start_transaction(extent_root, 1);
-	ret = btrfs_search_slot(trans, extent_root, extent_key, path, -1, 1);
-	if (ret > 0) {
-		ret = -EIO;
-		goto out;
-	}
-	if (ret < 0)
-		goto out;
-	ret = btrfs_del_item(trans, extent_root, path);
-out:
-	btrfs_end_transaction(trans, extent_root);
-	return ret;
-}
-
-static int noinline relocate_one_extent(struct btrfs_root *extent_root,
-					struct btrfs_path *path,
-					struct btrfs_key *extent_key)
-{
 	struct btrfs_key key;
 	struct btrfs_key found_key;
-	struct extent_buffer *leaf;
-	u64 last_file_objectid = 0;
-	u64 last_file_root = 0;
-	u64 last_file_offset = (u64)-1;
-	u64 last_extent = 0;
+	u64 bytenr;
 	u32 nritems;
-	u32 item_size;
-	int ret = 0;
+	int level;
+	int ret = 1;
 
-	if (extent_key->objectid == 0) {
-		ret = del_extent_zero(extent_root, path, extent_key);
-		goto out;
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	mutex_lock(&extent_root->fs_info->alloc_mutex);
+
+	if (first_time) {
+		ref_path->lowest_level = -1;
+		ref_path->current_level = -1;
+		goto walk_up;
 	}
-	key.objectid = extent_key->objectid;
-	key.type = BTRFS_EXTENT_REF_KEY;
-	key.offset = 0;
+walk_down:
+	level = ref_path->current_level - 1;
+	while (level >= -1) {
+		u64 parent;
+		if (level < ref_path->lowest_level)
+			break;
 
-	while(1) {
-		ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
+		if (level >= 0) {
+			bytenr = ref_path->nodes[level];
+		} else {
+			bytenr = ref_path->extent_start;
+		}
+		BUG_ON(bytenr == 0);
 
+		parent = ref_path->nodes[level + 1];
+		ref_path->nodes[level + 1] = 0;
+		ref_path->current_level = level;
+		BUG_ON(parent == 0);
+
+		key.objectid = bytenr;
+		key.offset = parent + 1;
+		key.type = BTRFS_EXTENT_REF_KEY;
+
+		ret = btrfs_search_slot(trans, extent_root, &key, path, 0, 0);
 		if (ret < 0)
 			goto out;
+		BUG_ON(ret == 0);
 
-		ret = 0;
 		leaf = path->nodes[0];
 		nritems = btrfs_header_nritems(leaf);
-		if (path->slots[0] == nritems) {
+		if (path->slots[0] >= nritems) {
 			ret = btrfs_next_leaf(extent_root, path);
-			if (ret > 0) {
-				ret = 0;
-				goto out;
-			}
 			if (ret < 0)
 				goto out;
+			if (ret > 0)
+				goto next;
 			leaf = path->nodes[0];
 		}
 
 		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-		if (found_key.objectid != extent_key->objectid) {
-			break;
+		if (found_key.objectid == bytenr &&
+				found_key.type == BTRFS_EXTENT_REF_KEY)
+			goto found;
+next:
+		level--;
+		btrfs_release_path(extent_root, path);
+		if (need_resched()) {
+			mutex_unlock(&extent_root->fs_info->alloc_mutex);
+			cond_resched();
+			mutex_lock(&extent_root->fs_info->alloc_mutex);
 		}
-
-		if (found_key.type != BTRFS_EXTENT_REF_KEY) {
-			break;
+	}
+	/* reached lowest level */
+	ret = 1;
+	goto out;
+walk_up:
+	level = ref_path->current_level;
+	while (level < BTRFS_MAX_LEVEL - 1) {
+		u64 ref_objectid;
+		if (level >= 0) {
+			bytenr = ref_path->nodes[level];
+		} else {
+			bytenr = ref_path->extent_start;
 		}
+		BUG_ON(bytenr == 0);
 
-		key.offset = found_key.offset + 1;
-		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+		key.objectid = bytenr;
+		key.offset = 0;
+		key.type = BTRFS_EXTENT_REF_KEY;
 
-		ret = relocate_one_reference(extent_root, path, extent_key,
-					     &last_file_objectid,
-					     &last_file_offset,
-					     &last_file_root, last_extent);
-		if (ret)
+		ret = btrfs_search_slot(trans, extent_root, &key, path, 0, 0);
+		if (ret < 0)
 			goto out;
-		last_extent = extent_key->objectid;
+
+		leaf = path->nodes[0];
+		nritems = btrfs_header_nritems(leaf);
+		if (path->slots[0] >= nritems) {
+			ret = btrfs_next_leaf(extent_root, path);
+			if (ret < 0)
+				goto out;
+			if (ret > 0) {
+				/* the extent was freed by someone */
+				if (ref_path->lowest_level == level)
+					goto out;
+				btrfs_release_path(extent_root, path);
+				goto walk_down;
+			}
+			leaf = path->nodes[0];
+		}
+
+		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+		if (found_key.objectid != bytenr ||
+				found_key.type != BTRFS_EXTENT_REF_KEY) {
+			/* the extent was freed by someone */
+			if (ref_path->lowest_level == level) {
+				ret = 1;
+				goto out;
+			}
+			btrfs_release_path(extent_root, path);
+			goto walk_down;
+		}
+found:
+		ref = btrfs_item_ptr(leaf, path->slots[0],
+				struct btrfs_extent_ref);
+		ref_objectid = btrfs_ref_objectid(leaf, ref);
+		if (ref_objectid < BTRFS_FIRST_FREE_OBJECTID) {
+			if (first_time) {
+				level = (int)ref_objectid;
+				BUG_ON(level >= BTRFS_MAX_LEVEL);
+				ref_path->lowest_level = level;
+				ref_path->current_level = level;
+				ref_path->nodes[level] = bytenr;
+			} else {
+				WARN_ON(ref_objectid != level);
+			}
+		} else {
+			WARN_ON(level != -1);
+		}
+		first_time = 0;
+
+		if (ref_path->lowest_level == level) {
+			ref_path->owner_objectid = ref_objectid;
+			ref_path->owner_offset = btrfs_ref_offset(leaf, ref);
+			ref_path->num_refs = btrfs_ref_num_refs(leaf, ref);
+		}
+
+		/*
+		 * the block is tree root or the block isn't in reference
+		 * counted tree.
+		 */
+		if (found_key.objectid == found_key.offset ||
+		    is_cowonly_root(btrfs_ref_root(leaf, ref))) {
+			ref_path->root_objectid = btrfs_ref_root(leaf, ref);
+			ref_path->root_generation =
+				btrfs_ref_generation(leaf, ref);
+			if (level < 0) {
+				/* special reference from the tree log */
+				ref_path->nodes[0] = found_key.offset;
+				ref_path->current_level = 0;
+			}
+			ret = 0;
+			goto out;
+		}
+
+		level++;
+		BUG_ON(ref_path->nodes[level] != 0);
+		ref_path->nodes[level] = found_key.offset;
+		ref_path->current_level = level;
+
+		/*
+		 * the reference was created in the running transaction,
+		 * no need to continue walking up.
+		 */
+		if (btrfs_ref_generation(leaf, ref) == trans->transid) {
+			ref_path->root_objectid = btrfs_ref_root(leaf, ref);
+			ref_path->root_generation =
+				btrfs_ref_generation(leaf, ref);
+			ret = 0;
+			goto out;
+		}
+
+		btrfs_release_path(extent_root, path);
+		if (need_resched()) {
+			mutex_unlock(&extent_root->fs_info->alloc_mutex);
+			cond_resched();
+			mutex_lock(&extent_root->fs_info->alloc_mutex);
+		}
+	}
+	/* reached max tree level, but no tree root found. */
+	BUG();
+out:
+	mutex_unlock(&extent_root->fs_info->alloc_mutex);
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int btrfs_first_ref_path(struct btrfs_trans_handle *trans,
+				struct btrfs_root *extent_root,
+				struct btrfs_ref_path *ref_path,
+				u64 extent_start)
+{
+	memset(ref_path, 0, sizeof(*ref_path));
+	ref_path->extent_start = extent_start;
+
+	return __next_ref_path(trans, extent_root, ref_path, 1);
+}
+
+static int btrfs_next_ref_path(struct btrfs_trans_handle *trans,
+			       struct btrfs_root *extent_root,
+			       struct btrfs_ref_path *ref_path)
+{
+	return __next_ref_path(trans, extent_root, ref_path, 0);
+}
+
+static int noinline get_new_locations(struct inode *reloc_inode,
+				      struct btrfs_key *extent_key,
+				      u64 offset, int no_fragment,
+				      struct disk_extent **extents,
+				      int *nr_extents)
+{
+	struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
+	struct btrfs_path *path;
+	struct btrfs_file_extent_item *fi;
+	struct extent_buffer *leaf;
+	struct disk_extent *exts = *extents;
+	struct btrfs_key found_key;
+	u64 cur_pos;
+	u64 last_byte;
+	u32 nritems;
+	int nr = 0;
+	int max = *nr_extents;
+	int ret;
+
+	WARN_ON(!no_fragment && *extents);
+	if (!exts) {
+		max = 1;
+		exts = kmalloc(sizeof(*exts) * max, GFP_NOFS);
+		if (!exts)
+			return -ENOMEM;
+	}
+
+	path = btrfs_alloc_path();
+	BUG_ON(!path);
+
+	cur_pos = extent_key->objectid - offset;
+	last_byte = extent_key->objectid + extent_key->offset;
+	ret = btrfs_lookup_file_extent(NULL, root, path, reloc_inode->i_ino,
+				       cur_pos, 0);
+	if (ret < 0)
+		goto out;
+	if (ret > 0) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	while (1) {
+		leaf = path->nodes[0];
+		nritems = btrfs_header_nritems(leaf);
+		if (path->slots[0] >= nritems) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				goto out;
+			if (ret > 0)
+				break;
+			leaf = path->nodes[0];
+		}
+
+		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+		if (found_key.offset != cur_pos ||
+		    found_key.type != BTRFS_EXTENT_DATA_KEY ||
+		    found_key.objectid != reloc_inode->i_ino)
+			break;
+
+		fi = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_file_extent_item);
+		if (btrfs_file_extent_type(leaf, fi) !=
+		    BTRFS_FILE_EXTENT_REG ||
+		    btrfs_file_extent_disk_bytenr(leaf, fi) == 0)
+			break;
+
+		if (nr == max) {
+			struct disk_extent *old = exts;
+			max *= 2;
+			exts = kzalloc(sizeof(*exts) * max, GFP_NOFS);
+			memcpy(exts, old, sizeof(*exts) * nr);
+			if (old != *extents)
+				kfree(old);
+		}
+
+		exts[nr].disk_bytenr =
+			btrfs_file_extent_disk_bytenr(leaf, fi);
+		exts[nr].disk_num_bytes =
+			btrfs_file_extent_disk_num_bytes(leaf, fi);
+		exts[nr].offset = btrfs_file_extent_offset(leaf, fi);
+		exts[nr].num_bytes = btrfs_file_extent_num_bytes(leaf, fi);
+		WARN_ON(exts[nr].offset > 0);
+		WARN_ON(exts[nr].num_bytes != exts[nr].disk_num_bytes);
+
+		cur_pos += exts[nr].num_bytes;
+		nr++;
+
+		if (cur_pos + offset >= last_byte)
+			break;
+
+		if (no_fragment) {
+			ret = 1;
+			goto out;
+		}
+		path->slots[0]++;
+	}
+
+	WARN_ON(cur_pos + offset > last_byte);
+	if (cur_pos + offset < last_byte) {
+		ret = -ENOENT;
+		goto out;
 	}
 	ret = 0;
 out:
+	btrfs_free_path(path);
+	if (ret) {
+		if (exts != *extents)
+			kfree(exts);
+	} else {
+		*extents = exts;
+		*nr_extents = nr;
+	}
+	return ret;
+}
+
+static int noinline replace_one_extent(struct btrfs_trans_handle *trans,
+					struct btrfs_root *root,
+					struct btrfs_path *path,
+					struct btrfs_key *extent_key,
+					struct btrfs_key *leaf_key,
+					struct btrfs_ref_path *ref_path,
+					struct disk_extent *new_extents,
+					int nr_extents)
+{
+	struct extent_buffer *leaf;
+	struct btrfs_file_extent_item *fi;
+	struct inode *inode = NULL;
+	struct btrfs_key key;
+	u64 lock_start = 0;
+	u64 lock_end = 0;
+	u64 num_bytes;
+	u64 ext_offset;
+	u64 first_pos;
+	u32 nritems;
+	int extent_locked = 0;
+	int ret;
+
+	first_pos = ref_path->owner_offset;
+	if (ref_path->owner_objectid != BTRFS_MULTIPLE_OBJECTIDS) {
+		key.objectid = ref_path->owner_objectid;
+		key.offset = ref_path->owner_offset;
+		key.type = BTRFS_EXTENT_DATA_KEY;
+	} else {
+		memcpy(&key, leaf_key, sizeof(key));
+	}
+
+	while (1) {
+		ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+		if (ret < 0)
+			goto out;
+
+		leaf = path->nodes[0];
+		nritems = btrfs_header_nritems(leaf);
+next:
+		if (extent_locked && ret > 0) {
+			/*
+			 * the file extent item was modified by someone
+			 * before the extent got locked.
+			 */
+			mutex_unlock(&BTRFS_I(inode)->extent_mutex);
+			unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
+				      lock_end, GFP_NOFS);
+			extent_locked = 0;
+		}
+
+		if (path->slots[0] >= nritems) {
+			if (ref_path->owner_objectid ==
+			    BTRFS_MULTIPLE_OBJECTIDS)
+				break;
+
+			BUG_ON(extent_locked);
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				goto out;
+			if (ret > 0)
+				break;
+			leaf = path->nodes[0];
+			nritems = btrfs_header_nritems(leaf);
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+
+		if (ref_path->owner_objectid != BTRFS_MULTIPLE_OBJECTIDS) {
+			if ((key.objectid > ref_path->owner_objectid) ||
+			    (key.objectid == ref_path->owner_objectid &&
+			     key.type > BTRFS_EXTENT_DATA_KEY) ||
+			    (key.offset >= first_pos + extent_key->offset))
+				break;
+		}
+
+		if (inode && key.objectid != inode->i_ino) {
+			BUG_ON(extent_locked);
+			btrfs_release_path(root, path);
+			mutex_unlock(&inode->i_mutex);
+			iput(inode);
+			inode = NULL;
+			continue;
+		}
+
+		if (key.type != BTRFS_EXTENT_DATA_KEY) {
+			path->slots[0]++;
+			ret = 1;
+			goto next;
+		}
+		fi = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_file_extent_item);
+		if ((btrfs_file_extent_type(leaf, fi) !=
+		     BTRFS_FILE_EXTENT_REG) ||
+		    (btrfs_file_extent_disk_bytenr(leaf, fi) !=
+		     extent_key->objectid)) {
+			path->slots[0]++;
+			ret = 1;
+			goto next;
+		}
+
+		num_bytes = btrfs_file_extent_num_bytes(leaf, fi);
+		ext_offset = btrfs_file_extent_offset(leaf, fi);
+
+		if (first_pos > key.offset - ext_offset)
+			first_pos = key.offset - ext_offset;
+
+		if (!extent_locked) {
+			lock_start = key.offset;
+			lock_end = lock_start + num_bytes - 1;
+		} else {
+			BUG_ON(lock_start != key.offset);
+			BUG_ON(lock_end - lock_start + 1 < num_bytes);
+		}
+
+		if (!inode) {
+			btrfs_release_path(root, path);
+
+			inode = btrfs_iget_locked(root->fs_info->sb,
+						  key.objectid, root);
+			if (inode->i_state & I_NEW) {
+				BTRFS_I(inode)->root = root;
+				BTRFS_I(inode)->location.objectid =
+					key.objectid;
+				BTRFS_I(inode)->location.type =
+					BTRFS_INODE_ITEM_KEY;
+				BTRFS_I(inode)->location.offset = 0;
+				btrfs_read_locked_inode(inode);
+				unlock_new_inode(inode);
+			}
+			/*
+			 * some code call btrfs_commit_transaction while
+			 * holding the i_mutex, so we can't use mutex_lock
+			 * here.
+			 */
+			if (is_bad_inode(inode) ||
+			    !mutex_trylock(&inode->i_mutex)) {
+				iput(inode);
+				inode = NULL;
+				key.offset = (u64)-1;
+				goto skip;
+			}
+		}
+
+		if (!extent_locked) {
+			struct btrfs_ordered_extent *ordered;
+
+			btrfs_release_path(root, path);
+
+			lock_extent(&BTRFS_I(inode)->io_tree, lock_start,
+				    lock_end, GFP_NOFS);
+			ordered = btrfs_lookup_first_ordered_extent(inode,
+								    lock_end);
+			if (ordered &&
+			    ordered->file_offset <= lock_end &&
+			    ordered->file_offset + ordered->len > lock_start) {
+				unlock_extent(&BTRFS_I(inode)->io_tree,
+					      lock_start, lock_end, GFP_NOFS);
+				btrfs_start_ordered_extent(inode, ordered, 1);
+				btrfs_put_ordered_extent(ordered);
+				key.offset += num_bytes;
+				goto skip;
+			}
+			if (ordered)
+				btrfs_put_ordered_extent(ordered);
+
+			mutex_lock(&BTRFS_I(inode)->extent_mutex);
+			extent_locked = 1;
+			continue;
+		}
+
+		if (nr_extents == 1) {
+			/* update extent pointer in place */
+			btrfs_set_file_extent_generation(leaf, fi,
+						trans->transid);
+			btrfs_set_file_extent_disk_bytenr(leaf, fi,
+						new_extents[0].disk_bytenr);
+			btrfs_set_file_extent_disk_num_bytes(leaf, fi,
+						new_extents[0].disk_num_bytes);
+			ext_offset += new_extents[0].offset;
+			btrfs_set_file_extent_offset(leaf, fi, ext_offset);
+			btrfs_mark_buffer_dirty(leaf);
+
+			btrfs_drop_extent_cache(inode, key.offset,
+						key.offset + num_bytes - 1, 0);
+
+			ret = btrfs_inc_extent_ref(trans, root,
+						new_extents[0].disk_bytenr,
+						new_extents[0].disk_num_bytes,
+						leaf->start,
+						root->root_key.objectid,
+						trans->transid,
+						key.objectid, key.offset);
+			BUG_ON(ret);
+
+			ret = btrfs_free_extent(trans, root,
+						extent_key->objectid,
+						extent_key->offset,
+						leaf->start,
+						btrfs_header_owner(leaf),
+						btrfs_header_generation(leaf),
+						key.objectid, key.offset, 0);
+			BUG_ON(ret);
+
+			btrfs_release_path(root, path);
+			key.offset += num_bytes;
+		} else {
+			u64 alloc_hint;
+			u64 extent_len;
+			int i;
+			/*
+			 * drop old extent pointer at first, then insert the
+			 * new pointers one bye one
+			 */
+			btrfs_release_path(root, path);
+			ret = btrfs_drop_extents(trans, root, inode, key.offset,
+						 key.offset + num_bytes,
+						 key.offset, &alloc_hint);
+			BUG_ON(ret);
+
+			for (i = 0; i < nr_extents; i++) {
+				if (ext_offset >= new_extents[i].num_bytes) {
+					ext_offset -= new_extents[i].num_bytes;
+					continue;
+				}
+				extent_len = min(new_extents[i].num_bytes -
+						 ext_offset, num_bytes);
+
+				ret = btrfs_insert_empty_item(trans, root,
+							      path, &key,
+							      sizeof(*fi));
+				BUG_ON(ret);
+
+				leaf = path->nodes[0];
+				fi = btrfs_item_ptr(leaf, path->slots[0],
+						struct btrfs_file_extent_item);
+				btrfs_set_file_extent_generation(leaf, fi,
+							trans->transid);
+				btrfs_set_file_extent_type(leaf, fi,
+							BTRFS_FILE_EXTENT_REG);
+				btrfs_set_file_extent_disk_bytenr(leaf, fi,
+						new_extents[i].disk_bytenr);
+				btrfs_set_file_extent_disk_num_bytes(leaf, fi,
+						new_extents[i].disk_num_bytes);
+				btrfs_set_file_extent_num_bytes(leaf, fi,
+							extent_len);
+				ext_offset += new_extents[i].offset;
+				btrfs_set_file_extent_offset(leaf, fi,
+							ext_offset);
+				btrfs_mark_buffer_dirty(leaf);
+
+				btrfs_drop_extent_cache(inode, key.offset,
+						key.offset + extent_len - 1, 0);
+
+				ret = btrfs_inc_extent_ref(trans, root,
+						new_extents[i].disk_bytenr,
+						new_extents[i].disk_num_bytes,
+						leaf->start,
+						root->root_key.objectid,
+						trans->transid,
+						key.objectid, key.offset);
+				BUG_ON(ret);
+				btrfs_release_path(root, path);
+
+				inode->i_blocks += extent_len >> 9;
+
+				ext_offset = 0;
+				num_bytes -= extent_len;
+				key.offset += extent_len;
+
+				if (num_bytes == 0)
+					break;
+			}
+			BUG_ON(i >= nr_extents);
+		}
+
+		if (extent_locked) {
+			mutex_unlock(&BTRFS_I(inode)->extent_mutex);
+			unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
+				      lock_end, GFP_NOFS);
+			extent_locked = 0;
+		}
+skip:
+		if (ref_path->owner_objectid != BTRFS_MULTIPLE_OBJECTIDS &&
+		    key.offset >= first_pos + extent_key->offset)
+			break;
+
+		cond_resched();
+	}
+	ret = 0;
+out:
+	btrfs_release_path(root, path);
+	if (inode) {
+		mutex_unlock(&inode->i_mutex);
+		if (extent_locked) {
+			mutex_unlock(&BTRFS_I(inode)->extent_mutex);
+			unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
+				      lock_end, GFP_NOFS);
+		}
+		iput(inode);
+	}
+	return ret;
+}
+
+int btrfs_add_reloc_mapping(struct btrfs_root *root, u64 orig_bytenr,
+			    u64 num_bytes, u64 new_bytenr)
+{
+	set_extent_bits(&root->fs_info->reloc_mapping_tree,
+			orig_bytenr, orig_bytenr + num_bytes - 1,
+			EXTENT_LOCKED, GFP_NOFS);
+	set_state_private(&root->fs_info->reloc_mapping_tree,
+			  orig_bytenr, new_bytenr);
+	return 0;
+}
+
+int btrfs_get_reloc_mapping(struct btrfs_root *root, u64 orig_bytenr,
+			    u64 num_bytes, u64 *new_bytenr)
+{
+	u64 bytenr;
+	u64 cur_bytenr = orig_bytenr;
+	u64 prev_bytenr = orig_bytenr;
+	int ret;
+
+	while (1) {
+		ret = get_state_private(&root->fs_info->reloc_mapping_tree,
+					cur_bytenr, &bytenr);
+		if (ret)
+			break;
+		prev_bytenr = cur_bytenr;
+		cur_bytenr = bytenr;
+	}
+
+	if (orig_bytenr == cur_bytenr)
+		return -ENOENT;
+
+	if (prev_bytenr != orig_bytenr) {
+		set_state_private(&root->fs_info->reloc_mapping_tree,
+				  orig_bytenr, cur_bytenr);
+	}
+	*new_bytenr = cur_bytenr;
+	return 0;
+}
+
+void btrfs_free_reloc_mappings(struct btrfs_root *root)
+{
+	clear_extent_bits(&root->fs_info->reloc_mapping_tree,
+			  0, (u64)-1, -1, GFP_NOFS);
+}
+
+int btrfs_reloc_tree_cache_ref(struct btrfs_trans_handle *trans,
+			       struct btrfs_root *root,
+			       struct extent_buffer *buf, u64 orig_start)
+{
+	int level;
+	int ret;
+
+	BUG_ON(btrfs_header_generation(buf) != trans->transid);
+	BUG_ON(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
+
+	level = btrfs_header_level(buf);
+	if (level == 0) {
+		struct btrfs_leaf_ref *ref;
+		struct btrfs_leaf_ref *orig_ref;
+
+		orig_ref = btrfs_lookup_leaf_ref(root, orig_start);
+		if (!orig_ref)
+			return -ENOENT;
+
+		ref = btrfs_alloc_leaf_ref(root, orig_ref->nritems);
+		if (!ref) {
+			btrfs_free_leaf_ref(root, orig_ref);
+			return -ENOMEM;
+		}
+
+		ref->nritems = orig_ref->nritems;
+		memcpy(ref->extents, orig_ref->extents,
+			sizeof(ref->extents[0]) * ref->nritems);
+
+		btrfs_free_leaf_ref(root, orig_ref);
+
+		ref->root_gen = trans->transid;
+		ref->bytenr = buf->start;
+		ref->owner = btrfs_header_owner(buf);
+		ref->generation = btrfs_header_generation(buf);
+		ret = btrfs_add_leaf_ref(root, ref, 0);
+		WARN_ON(ret);
+		btrfs_free_leaf_ref(root, ref);
+	}
+	return 0;
+}
+
+static int noinline invalidate_extent_cache(struct btrfs_root *root,
+					struct extent_buffer *leaf,
+					struct btrfs_block_group_cache *group,
+					struct btrfs_root *target_root)
+{
+	struct btrfs_key key;
+	struct inode *inode = NULL;
+	struct btrfs_file_extent_item *fi;
+	u64 num_bytes;
+	u64 skip_objectid = 0;
+	u32 nritems;
+	u32 i;
+
+	nritems = btrfs_header_nritems(leaf);
+	for (i = 0; i < nritems; i++) {
+		btrfs_item_key_to_cpu(leaf, &key, i);
+		if (key.objectid == skip_objectid ||
+		    key.type != BTRFS_EXTENT_DATA_KEY)
+			continue;
+		fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
+		if (btrfs_file_extent_type(leaf, fi) ==
+		    BTRFS_FILE_EXTENT_INLINE)
+			continue;
+		if (btrfs_file_extent_disk_bytenr(leaf, fi) == 0)
+			continue;
+		if (!inode || inode->i_ino != key.objectid) {
+			iput(inode);
+			inode = btrfs_ilookup(target_root->fs_info->sb,
+					      key.objectid, target_root, 1);
+		}
+		if (!inode) {
+			skip_objectid = key.objectid;
+			continue;
+		}
+		num_bytes = btrfs_file_extent_num_bytes(leaf, fi);
+
+		lock_extent(&BTRFS_I(inode)->io_tree, key.offset,
+			    key.offset + num_bytes - 1, GFP_NOFS);
+		mutex_lock(&BTRFS_I(inode)->extent_mutex);
+		btrfs_drop_extent_cache(inode, key.offset,
+					key.offset + num_bytes - 1, 1);
+		mutex_unlock(&BTRFS_I(inode)->extent_mutex);
+		unlock_extent(&BTRFS_I(inode)->io_tree, key.offset,
+			      key.offset + num_bytes - 1, GFP_NOFS);
+		cond_resched();
+	}
+	iput(inode);
+	return 0;
+}
+
+static int noinline replace_extents_in_leaf(struct btrfs_trans_handle *trans,
+					struct btrfs_root *root,
+					struct extent_buffer *leaf,
+					struct btrfs_block_group_cache *group,
+					struct inode *reloc_inode)
+{
+	struct btrfs_key key;
+	struct btrfs_key extent_key;
+	struct btrfs_file_extent_item *fi;
+	struct btrfs_leaf_ref *ref;
+	struct disk_extent *new_extent;
+	u64 bytenr;
+	u64 num_bytes;
+	u32 nritems;
+	u32 i;
+	int ext_index;
+	int nr_extent;
+	int ret;
+
+	new_extent = kmalloc(sizeof(*new_extent), GFP_NOFS);
+	BUG_ON(!new_extent);
+
+	ref = btrfs_lookup_leaf_ref(root, leaf->start);
+	BUG_ON(!ref);
+
+	ext_index = -1;
+	nritems = btrfs_header_nritems(leaf);
+	for (i = 0; i < nritems; i++) {
+		btrfs_item_key_to_cpu(leaf, &key, i);
+		if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
+			continue;
+		fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
+		if (btrfs_file_extent_type(leaf, fi) ==
+		    BTRFS_FILE_EXTENT_INLINE)
+			continue;
+		bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+		num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
+		if (bytenr == 0)
+			continue;
+
+		ext_index++;
+		if (bytenr >= group->key.objectid + group->key.offset ||
+		    bytenr + num_bytes <= group->key.objectid)
+			continue;
+
+		extent_key.objectid = bytenr;
+		extent_key.offset = num_bytes;
+		extent_key.type = BTRFS_EXTENT_ITEM_KEY;
+		nr_extent = 1;
+		ret = get_new_locations(reloc_inode, &extent_key,
+					group->key.objectid, 1,
+					&new_extent, &nr_extent);
+		if (ret > 0)
+			continue;
+		BUG_ON(ret < 0);
+
+		BUG_ON(ref->extents[ext_index].bytenr != bytenr);
+		BUG_ON(ref->extents[ext_index].num_bytes != num_bytes);
+		ref->extents[ext_index].bytenr = new_extent->disk_bytenr;
+		ref->extents[ext_index].num_bytes = new_extent->disk_num_bytes;
+
+		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
+		btrfs_set_file_extent_disk_bytenr(leaf, fi,
+						new_extent->disk_bytenr);
+		btrfs_set_file_extent_disk_num_bytes(leaf, fi,
+						new_extent->disk_num_bytes);
+		new_extent->offset += btrfs_file_extent_offset(leaf, fi);
+		btrfs_set_file_extent_offset(leaf, fi, new_extent->offset);
+		btrfs_mark_buffer_dirty(leaf);
+
+		ret = btrfs_inc_extent_ref(trans, root,
+					new_extent->disk_bytenr,
+					new_extent->disk_num_bytes,
+					leaf->start,
+					root->root_key.objectid,
+					trans->transid,
+					key.objectid, key.offset);
+		BUG_ON(ret);
+		ret = btrfs_free_extent(trans, root,
+					bytenr, num_bytes, leaf->start,
+					btrfs_header_owner(leaf),
+					btrfs_header_generation(leaf),
+					key.objectid, key.offset, 0);
+		BUG_ON(ret);
+		cond_resched();
+	}
+	kfree(new_extent);
+	BUG_ON(ext_index + 1 != ref->nritems);
+	btrfs_free_leaf_ref(root, ref);
+	return 0;
+}
+
+int btrfs_free_reloc_root(struct btrfs_root *root)
+{
+	struct btrfs_root *reloc_root;
+
+	if (root->reloc_root) {
+		reloc_root = root->reloc_root;
+		root->reloc_root = NULL;
+		list_add(&reloc_root->dead_list,
+			 &root->fs_info->dead_reloc_roots);
+	}
+	return 0;
+}
+
+int btrfs_drop_dead_reloc_roots(struct btrfs_root *root)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *reloc_root;
+	struct btrfs_root *prev_root = NULL;
+	struct list_head dead_roots;
+	int ret;
+	unsigned long nr;
+
+	INIT_LIST_HEAD(&dead_roots);
+	list_splice_init(&root->fs_info->dead_reloc_roots, &dead_roots);
+
+	while (!list_empty(&dead_roots)) {
+		reloc_root = list_entry(dead_roots.prev,
+					struct btrfs_root, dead_list);
+		list_del_init(&reloc_root->dead_list);
+
+		BUG_ON(reloc_root->commit_root != NULL);
+		while (1) {
+			trans = btrfs_join_transaction(root, 1);
+			BUG_ON(!trans);
+
+			mutex_lock(&root->fs_info->drop_mutex);
+			ret = btrfs_drop_snapshot(trans, reloc_root);
+			if (ret != -EAGAIN)
+				break;
+			mutex_unlock(&root->fs_info->drop_mutex);
+
+			nr = trans->blocks_used;
+			ret = btrfs_end_transaction(trans, root);
+			BUG_ON(ret);
+			btrfs_btree_balance_dirty(root, nr);
+		}
+
+		free_extent_buffer(reloc_root->node);
+
+		ret = btrfs_del_root(trans, root->fs_info->tree_root,
+				     &reloc_root->root_key);
+		BUG_ON(ret);
+		mutex_unlock(&root->fs_info->drop_mutex);
+
+		nr = trans->blocks_used;
+		ret = btrfs_end_transaction(trans, root);
+		BUG_ON(ret);
+		btrfs_btree_balance_dirty(root, nr);
+
+		kfree(prev_root);
+		prev_root = reloc_root;
+	}
+	if (prev_root) {
+		btrfs_remove_leaf_refs(prev_root, (u64)-1, 0);
+		kfree(prev_root);
+	}
+	return 0;
+}
+
+int btrfs_add_dead_reloc_root(struct btrfs_root *root)
+{
+	list_add(&root->dead_list, &root->fs_info->dead_reloc_roots);
+	return 0;
+}
+
+int btrfs_cleanup_reloc_trees(struct btrfs_root *root)
+{
+	struct btrfs_root *reloc_root;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_key location;
+	int found;
+	int ret;
+
+	mutex_lock(&root->fs_info->tree_reloc_mutex);
+	ret = btrfs_find_dead_roots(root, BTRFS_TREE_RELOC_OBJECTID, NULL);
+	BUG_ON(ret);
+	found = !list_empty(&root->fs_info->dead_reloc_roots);
+	mutex_unlock(&root->fs_info->tree_reloc_mutex);
+
+	if (found) {
+		trans = btrfs_start_transaction(root, 1);
+		BUG_ON(!trans);
+		ret = btrfs_commit_transaction(trans, root);
+		BUG_ON(ret);
+	}
+
+	location.objectid = BTRFS_DATA_RELOC_TREE_OBJECTID;
+	location.offset = (u64)-1;
+	location.type = BTRFS_ROOT_ITEM_KEY;
+
+	reloc_root = btrfs_read_fs_root_no_name(root->fs_info, &location);
+	BUG_ON(!reloc_root);
+	btrfs_orphan_cleanup(reloc_root);
+	return 0;
+}
+
+static int noinline init_reloc_tree(struct btrfs_trans_handle *trans,
+				    struct btrfs_root *root)
+{
+	struct btrfs_root *reloc_root;
+	struct extent_buffer *eb;
+	struct btrfs_root_item *root_item;
+	struct btrfs_key root_key;
+	int ret;
+
+	BUG_ON(!root->ref_cows);
+	if (root->reloc_root)
+		return 0;
+
+	root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
+	BUG_ON(!root_item);
+
+	ret = btrfs_copy_root(trans, root, root->commit_root,
+			      &eb, BTRFS_TREE_RELOC_OBJECTID);
+	BUG_ON(ret);
+
+	root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
+	root_key.offset = root->root_key.objectid;
+	root_key.type = BTRFS_ROOT_ITEM_KEY;
+
+	memcpy(root_item, &root->root_item, sizeof(root_item));
+	btrfs_set_root_refs(root_item, 0);
+	btrfs_set_root_bytenr(root_item, eb->start);
+	btrfs_set_root_level(root_item, btrfs_header_level(eb));
+	memset(&root_item->drop_progress, 0, sizeof(root_item->drop_progress));
+	root_item->drop_level = 0;
+
+	btrfs_tree_unlock(eb);
+	free_extent_buffer(eb);
+
+	ret = btrfs_insert_root(trans, root->fs_info->tree_root,
+				&root_key, root_item);
+	BUG_ON(ret);
+	kfree(root_item);
+
+	reloc_root = btrfs_read_fs_root_no_radix(root->fs_info->tree_root,
+						 &root_key);
+	BUG_ON(!reloc_root);
+	reloc_root->last_trans = trans->transid;
+	reloc_root->commit_root = NULL;
+	reloc_root->ref_tree = &root->fs_info->reloc_ref_tree;
+
+	root->reloc_root = reloc_root;
+	return 0;
+}
+
+/*
+ * Core function of space balance.
+ *
+ * The idea is using reloc trees to relocate tree blocks in reference
+ * counted roots. There is one reloc tree for each subvol, all reloc
+ * trees share same key objectid. Reloc trees are snapshots of the
+ * latest committed roots (subvol root->commit_root). To relocate a tree
+ * block referenced by a subvol, the code COW the block through the reloc
+ * tree, then update pointer in the subvol to point to the new block.
+ * Since all reloc trees share same key objectid, we can easily do special
+ * handing to share tree blocks between reloc trees. Once a tree block has
+ * been COWed in one reloc tree, we can use the result when the same block
+ * is COWed again through other reloc trees.
+ */
+static int noinline relocate_one_path(struct btrfs_trans_handle *trans,
+				      struct btrfs_root *root,
+				      struct btrfs_path *path,
+				      struct btrfs_key *first_key,
+				      struct btrfs_ref_path *ref_path,
+				      struct btrfs_block_group_cache *group,
+				      struct inode *reloc_inode)
+{
+	struct btrfs_root *reloc_root;
+	struct extent_buffer *eb = NULL;
+	struct btrfs_key *keys;
+	u64 *nodes;
+	int level;
+	int lowest_merge;
+	int lowest_level = 0;
+	int update_refs;
+	int ret;
+
+	if (ref_path->owner_objectid < BTRFS_FIRST_FREE_OBJECTID)
+		lowest_level = ref_path->owner_objectid;
+
+	if (is_cowonly_root(ref_path->root_objectid)) {
+		path->lowest_level = lowest_level;
+		ret = btrfs_search_slot(trans, root, first_key, path, 0, 1);
+		BUG_ON(ret < 0);
+		path->lowest_level = 0;
+		btrfs_release_path(root, path);
+		return 0;
+	}
+
+	keys = kzalloc(sizeof(*keys) * BTRFS_MAX_LEVEL, GFP_NOFS);
+	BUG_ON(!keys);
+	nodes = kzalloc(sizeof(*nodes) * BTRFS_MAX_LEVEL, GFP_NOFS);
+	BUG_ON(!nodes);
+
+	mutex_lock(&root->fs_info->tree_reloc_mutex);
+	ret = init_reloc_tree(trans, root);
+	BUG_ON(ret);
+	reloc_root = root->reloc_root;
+
+	path->lowest_level = lowest_level;
+	ret = btrfs_search_slot(trans, reloc_root, first_key, path, 0, 0);
+	BUG_ON(ret);
+	/*
+	 * get relocation mapping for tree blocks in the path
+	 */
+	lowest_merge = BTRFS_MAX_LEVEL;
+	for (level = BTRFS_MAX_LEVEL - 1; level >= lowest_level; level--) {
+		u64 new_bytenr;
+		eb = path->nodes[level];
+		if (!eb || eb == reloc_root->node)
+			continue;
+		ret = btrfs_get_reloc_mapping(reloc_root, eb->start, eb->len,
+					      &new_bytenr);
+		if (ret)
+			continue;
+		if (level == 0)
+			btrfs_item_key_to_cpu(eb, &keys[level], 0);
+		else
+			btrfs_node_key_to_cpu(eb, &keys[level], 0);
+		nodes[level] = new_bytenr;
+		lowest_merge = level;
+	}
+
+	update_refs = 0;
+	if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
+		eb = path->nodes[0];
+		if (btrfs_header_generation(eb) < trans->transid)
+			update_refs = 1;
+	}
+
+	btrfs_release_path(reloc_root, path);
+	/*
+	 * merge tree blocks that already relocated in other reloc trees
+	 */
+	if (lowest_merge != BTRFS_MAX_LEVEL) {
+		ret = btrfs_merge_path(trans, reloc_root, keys, nodes,
+				       lowest_merge);
+		BUG_ON(ret < 0);
+	}
+	/*
+	 * cow any tree blocks that still haven't been relocated
+	 */
+	ret = btrfs_search_slot(trans, reloc_root, first_key, path, 0, 1);
+	BUG_ON(ret);
+	/*
+	 * if we are relocating data block group, update extent pointers
+	 * in the newly created tree leaf.
+	 */
+	eb = path->nodes[0];
+	if (update_refs && nodes[0] != eb->start) {
+		ret = replace_extents_in_leaf(trans, reloc_root, eb, group,
+					      reloc_inode);
+		BUG_ON(ret);
+	}
+
+	memset(keys, 0, sizeof(*keys) * BTRFS_MAX_LEVEL);
+	memset(nodes, 0, sizeof(*nodes) * BTRFS_MAX_LEVEL);
+	for (level = BTRFS_MAX_LEVEL - 1; level >= lowest_level; level--) {
+		eb = path->nodes[level];
+		if (!eb || eb == reloc_root->node)
+			continue;
+		BUG_ON(btrfs_header_owner(eb) != BTRFS_TREE_RELOC_OBJECTID);
+		nodes[level] = eb->start;
+		if (level == 0)
+			btrfs_item_key_to_cpu(eb, &keys[level], 0);
+		else
+			btrfs_node_key_to_cpu(eb, &keys[level], 0);
+	}
+
+	if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
+		eb = path->nodes[0];
+		extent_buffer_get(eb);
+	}
+	btrfs_release_path(reloc_root, path);
+	/*
+	 * replace tree blocks in the fs tree with tree blocks in
+	 * the reloc tree.
+	 */
+	ret = btrfs_merge_path(trans, root, keys, nodes, lowest_level);
+	BUG_ON(ret < 0);
+
+	if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
+		ret = invalidate_extent_cache(reloc_root, eb, group, root);
+		BUG_ON(ret);
+		free_extent_buffer(eb);
+	}
+	mutex_unlock(&root->fs_info->tree_reloc_mutex);
+
+	path->lowest_level = 0;
+	kfree(nodes);
+	kfree(keys);
+	return 0;
+}
+
+static int noinline relocate_tree_block(struct btrfs_trans_handle *trans,
+					struct btrfs_root *root,
+					struct btrfs_path *path,
+					struct btrfs_key *first_key,
+					struct btrfs_ref_path *ref_path)
+{
+	int ret;
+	int needs_lock = 0;
+
+	if (root == root->fs_info->extent_root ||
+	    root == root->fs_info->chunk_root ||
+	    root == root->fs_info->dev_root) {
+		needs_lock = 1;
+		mutex_lock(&root->fs_info->alloc_mutex);
+	}
+
+	ret = relocate_one_path(trans, root, path, first_key,
+				ref_path, NULL, NULL);
+	BUG_ON(ret);
+
+	if (root == root->fs_info->extent_root)
+		btrfs_extent_post_op(trans, root);
+	if (needs_lock)
+		mutex_unlock(&root->fs_info->alloc_mutex);
+
+	return 0;
+}
+
+static int noinline del_extent_zero(struct btrfs_trans_handle *trans,
+				    struct btrfs_root *extent_root,
+				    struct btrfs_path *path,
+				    struct btrfs_key *extent_key)
+{
+	int ret;
+
+	mutex_lock(&extent_root->fs_info->alloc_mutex);
+	ret = btrfs_search_slot(trans, extent_root, extent_key, path, -1, 1);
+	if (ret)
+		goto out;
+	ret = btrfs_del_item(trans, extent_root, path);
+out:
 	btrfs_release_path(extent_root, path);
+	mutex_unlock(&extent_root->fs_info->alloc_mutex);
+	return ret;
+}
+
+static struct btrfs_root noinline *read_ref_root(struct btrfs_fs_info *fs_info,
+						struct btrfs_ref_path *ref_path)
+{
+	struct btrfs_key root_key;
+
+	root_key.objectid = ref_path->root_objectid;
+	root_key.type = BTRFS_ROOT_ITEM_KEY;
+	if (is_cowonly_root(ref_path->root_objectid))
+		root_key.offset = 0;
+	else
+		root_key.offset = (u64)-1;
+
+	return btrfs_read_fs_root_no_name(fs_info, &root_key);
+}
+
+static int noinline relocate_one_extent(struct btrfs_root *extent_root,
+					struct btrfs_path *path,
+					struct btrfs_key *extent_key,
+					struct btrfs_block_group_cache *group,
+					struct inode *reloc_inode, int pass)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *found_root;
+	struct btrfs_ref_path *ref_path = NULL;
+	struct disk_extent *new_extents = NULL;
+	int nr_extents = 0;
+	int loops;
+	int ret;
+	int level;
+	struct btrfs_key first_key;
+	u64 prev_block = 0;
+
+	mutex_unlock(&extent_root->fs_info->alloc_mutex);
+
+	trans = btrfs_start_transaction(extent_root, 1);
+	BUG_ON(!trans);
+
+	if (extent_key->objectid == 0) {
+		ret = del_extent_zero(trans, extent_root, path, extent_key);
+		goto out;
+	}
+
+	ref_path = kmalloc(sizeof(*ref_path), GFP_NOFS);
+	if (!ref_path) {
+	       ret = -ENOMEM;
+	       goto out;
+	}
+
+	for (loops = 0; ; loops++) {
+		if (loops == 0) {
+			ret = btrfs_first_ref_path(trans, extent_root, ref_path,
+						   extent_key->objectid);
+		} else {
+			ret = btrfs_next_ref_path(trans, extent_root, ref_path);
+		}
+		if (ret < 0)
+			goto out;
+		if (ret > 0)
+			break;
+
+		if (ref_path->root_objectid == BTRFS_TREE_LOG_OBJECTID ||
+		    ref_path->root_objectid == BTRFS_TREE_RELOC_OBJECTID)
+			continue;
+
+		found_root = read_ref_root(extent_root->fs_info, ref_path);
+		BUG_ON(!found_root);
+		/*
+		 * for reference counted tree, only process reference paths
+		 * rooted at the latest committed root.
+		 */
+		if (found_root->ref_cows &&
+		    ref_path->root_generation != found_root->root_key.offset)
+			continue;
+
+		if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
+			if (pass == 0) {
+				/*
+				 * copy data extents to new locations
+				 */
+				u64 group_start = group->key.objectid;
+				ret = relocate_data_extent(reloc_inode,
+							   extent_key,
+							   group_start);
+				if (ret < 0)
+					goto out;
+				break;
+			}
+			level = 0;
+		} else {
+			level = ref_path->owner_objectid;
+		}
+
+		if (prev_block != ref_path->nodes[level]) {
+			struct extent_buffer *eb;
+			u64 block_start = ref_path->nodes[level];
+			u64 block_size = btrfs_level_size(found_root, level);
+
+			eb = read_tree_block(found_root, block_start,
+					     block_size, 0);
+			btrfs_tree_lock(eb);
+			BUG_ON(level != btrfs_header_level(eb));
+
+			if (level == 0)
+				btrfs_item_key_to_cpu(eb, &first_key, 0);
+			else
+				btrfs_node_key_to_cpu(eb, &first_key, 0);
+
+			btrfs_tree_unlock(eb);
+			free_extent_buffer(eb);
+			prev_block = block_start;
+		}
+
+		if (ref_path->owner_objectid >= BTRFS_FIRST_FREE_OBJECTID &&
+		    pass >= 2) {
+			/*
+			 * use fallback method to process the remaining
+			 * references.
+			 */
+			if (!new_extents) {
+				u64 group_start = group->key.objectid;
+				ret = get_new_locations(reloc_inode,
+							extent_key,
+							group_start, 0,
+							&new_extents,
+							&nr_extents);
+				if (ret < 0)
+					goto out;
+			}
+			btrfs_record_root_in_trans(found_root);
+			ret = replace_one_extent(trans, found_root,
+						path, extent_key,
+						&first_key, ref_path,
+						new_extents, nr_extents);
+			if (ret < 0)
+				goto out;
+			continue;
+		}
+
+		btrfs_record_root_in_trans(found_root);
+		if (ref_path->owner_objectid < BTRFS_FIRST_FREE_OBJECTID) {
+			ret = relocate_tree_block(trans, found_root, path,
+						  &first_key, ref_path);
+		} else {
+			/*
+			 * try to update data extent references while
+			 * keeping metadata shared between snapshots.
+			 */
+			ret = relocate_one_path(trans, found_root, path,
+						&first_key, ref_path,
+						group, reloc_inode);
+		}
+		if (ret < 0)
+			goto out;
+	}
+	ret = 0;
+out:
+	btrfs_end_transaction(trans, extent_root);
+	kfree(new_extents);
+	kfree(ref_path);
+	mutex_lock(&extent_root->fs_info->alloc_mutex);
 	return ret;
 }
 
@@ -3686,84 +4780,155 @@
 	return 0;
 }
 
-int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 shrink_start)
+static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
+				 struct btrfs_root *root,
+				 u64 objectid, u64 size)
+{
+	struct btrfs_path *path;
+	struct btrfs_inode_item *item;
+	struct extent_buffer *leaf;
+	int ret;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	ret = btrfs_insert_empty_inode(trans, root, path, objectid);
+	if (ret)
+		goto out;
+
+	leaf = path->nodes[0];
+	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
+	memset_extent_buffer(leaf, 0, (unsigned long)item, sizeof(*item));
+	btrfs_set_inode_generation(leaf, item, 1);
+	btrfs_set_inode_size(leaf, item, size);
+	btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
+	btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NODATASUM);
+	btrfs_mark_buffer_dirty(leaf);
+	btrfs_release_path(root, path);
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static struct inode noinline *create_reloc_inode(struct btrfs_fs_info *fs_info,
+					struct btrfs_block_group_cache *group)
+{
+	struct inode *inode = NULL;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *root;
+	struct btrfs_key root_key;
+	u64 objectid = BTRFS_FIRST_FREE_OBJECTID;
+	int err = 0;
+
+	root_key.objectid = BTRFS_DATA_RELOC_TREE_OBJECTID;
+	root_key.type = BTRFS_ROOT_ITEM_KEY;
+	root_key.offset = (u64)-1;
+	root = btrfs_read_fs_root_no_name(fs_info, &root_key);
+	if (IS_ERR(root))
+		return ERR_CAST(root);
+
+	trans = btrfs_start_transaction(root, 1);
+	BUG_ON(!trans);
+
+	err = btrfs_find_free_objectid(trans, root, objectid, &objectid);
+	if (err)
+		goto out;
+
+	err = __insert_orphan_inode(trans, root, objectid, group->key.offset);
+	BUG_ON(err);
+
+	err = btrfs_insert_file_extent(trans, root, objectid, 0, 0, 0,
+				       group->key.offset, 0);
+	BUG_ON(err);
+
+	inode = btrfs_iget_locked(root->fs_info->sb, objectid, root);
+	if (inode->i_state & I_NEW) {
+		BTRFS_I(inode)->root = root;
+		BTRFS_I(inode)->location.objectid = objectid;
+		BTRFS_I(inode)->location.type = BTRFS_INODE_ITEM_KEY;
+		BTRFS_I(inode)->location.offset = 0;
+		btrfs_read_locked_inode(inode);
+		unlock_new_inode(inode);
+		BUG_ON(is_bad_inode(inode));
+	} else {
+		BUG_ON(1);
+	}
+
+	err = btrfs_orphan_add(trans, inode);
+out:
+	btrfs_end_transaction(trans, root);
+	if (err) {
+		if (inode)
+			iput(inode);
+		inode = ERR_PTR(err);
+	}
+	return inode;
+}
+
+int btrfs_relocate_block_group(struct btrfs_root *root, u64 group_start)
 {
 	struct btrfs_trans_handle *trans;
-	struct btrfs_root *tree_root = root->fs_info->tree_root;
 	struct btrfs_path *path;
+	struct btrfs_fs_info *info = root->fs_info;
+	struct extent_buffer *leaf;
+	struct inode *reloc_inode;
+	struct btrfs_block_group_cache *block_group;
+	struct btrfs_key key;
 	u64 cur_byte;
 	u64 total_found;
-	u64 shrink_last_byte;
-	struct btrfs_block_group_cache *shrink_block_group;
-	struct btrfs_key key;
-	struct btrfs_key found_key;
-	struct extent_buffer *leaf;
 	u32 nritems;
 	int ret;
 	int progress;
+	int pass = 0;
 
-	mutex_lock(&root->fs_info->alloc_mutex);
-	shrink_block_group = btrfs_lookup_block_group(root->fs_info,
-						      shrink_start);
-	BUG_ON(!shrink_block_group);
-
-	shrink_last_byte = shrink_block_group->key.objectid +
-		shrink_block_group->key.offset;
-
-	shrink_block_group->space_info->total_bytes -=
-		shrink_block_group->key.offset;
-	path = btrfs_alloc_path();
 	root = root->fs_info->extent_root;
-	path->reada = 2;
+
+	block_group = btrfs_lookup_block_group(info, group_start);
+	BUG_ON(!block_group);
 
 	printk("btrfs relocating block group %llu flags %llu\n",
-	       (unsigned long long)shrink_start,
-	       (unsigned long long)shrink_block_group->flags);
+	       (unsigned long long)block_group->key.objectid,
+	       (unsigned long long)block_group->flags);
 
-	__alloc_chunk_for_shrink(root, shrink_block_group, 1);
+	path = btrfs_alloc_path();
+	BUG_ON(!path);
 
+	reloc_inode = create_reloc_inode(info, block_group);
+	BUG_ON(IS_ERR(reloc_inode));
+
+	mutex_lock(&root->fs_info->alloc_mutex);
+
+	__alloc_chunk_for_shrink(root, block_group, 1);
+	block_group->ro = 1;
+	block_group->space_info->total_bytes -= block_group->key.offset;
+
+	mutex_unlock(&root->fs_info->alloc_mutex);
+
+	btrfs_start_delalloc_inodes(info->tree_root);
+	btrfs_wait_ordered_extents(info->tree_root, 0);
 again:
-
-	shrink_block_group->ro = 1;
-
 	total_found = 0;
 	progress = 0;
-	key.objectid = shrink_start;
+	key.objectid = block_group->key.objectid;
 	key.offset = 0;
 	key.type = 0;
 	cur_byte = key.objectid;
 
-	mutex_unlock(&root->fs_info->alloc_mutex);
+	trans = btrfs_start_transaction(info->tree_root, 1);
+	btrfs_commit_transaction(trans, info->tree_root);
 
-	btrfs_start_delalloc_inodes(root);
-	btrfs_wait_ordered_extents(tree_root, 0);
+	mutex_lock(&root->fs_info->cleaner_mutex);
+	btrfs_clean_old_snapshots(info->tree_root);
+	btrfs_remove_leaf_refs(info->tree_root, (u64)-1, 1);
+	mutex_unlock(&root->fs_info->cleaner_mutex);
 
 	mutex_lock(&root->fs_info->alloc_mutex);
 
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
-
-	ret = btrfs_previous_item(root, path, 0, BTRFS_EXTENT_ITEM_KEY);
-	if (ret < 0)
-		goto out;
-
-	if (ret == 0) {
-		leaf = path->nodes[0];
-		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-		if (found_key.objectid + found_key.offset > shrink_start &&
-		    found_key.objectid < shrink_last_byte) {
-			cur_byte = found_key.objectid;
-			key.objectid = cur_byte;
-		}
-	}
-	btrfs_release_path(root, path);
-
 	while(1) {
 		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 		if (ret < 0)
 			goto out;
-
 next:
 		leaf = path->nodes[0];
 		nritems = btrfs_header_nritems(leaf);
@@ -3779,109 +4944,76 @@
 			nritems = btrfs_header_nritems(leaf);
 		}
 
-		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 
-		if (found_key.objectid >= shrink_last_byte)
+		if (key.objectid >= block_group->key.objectid +
+		    block_group->key.offset)
 			break;
 
 		if (progress && need_resched()) {
-			memcpy(&key, &found_key, sizeof(key));
-			cond_resched();
 			btrfs_release_path(root, path);
-			btrfs_search_slot(NULL, root, &key, path, 0, 0);
+			mutex_unlock(&root->fs_info->alloc_mutex);
+			cond_resched();
+			mutex_lock(&root->fs_info->alloc_mutex);
 			progress = 0;
-			goto next;
+			continue;
 		}
 		progress = 1;
 
-		if (btrfs_key_type(&found_key) != BTRFS_EXTENT_ITEM_KEY ||
-		    found_key.objectid + found_key.offset <= cur_byte) {
-			memcpy(&key, &found_key, sizeof(key));
-			key.offset++;
+		if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY ||
+		    key.objectid + key.offset <= cur_byte) {
 			path->slots[0]++;
 			goto next;
 		}
 
 		total_found++;
-		cur_byte = found_key.objectid + found_key.offset;
-		key.objectid = cur_byte;
+		cur_byte = key.objectid + key.offset;
 		btrfs_release_path(root, path);
-		ret = relocate_one_extent(root, path, &found_key);
-		__alloc_chunk_for_shrink(root, shrink_block_group, 0);
+
+		__alloc_chunk_for_shrink(root, block_group, 0);
+		ret = relocate_one_extent(root, path, &key, block_group,
+					  reloc_inode, pass);
+		BUG_ON(ret < 0);
+
+		key.objectid = cur_byte;
+		key.type = 0;
+		key.offset = 0;
 	}
 
 	btrfs_release_path(root, path);
+	mutex_unlock(&root->fs_info->alloc_mutex);
+
+	if (pass == 0) {
+		btrfs_wait_ordered_range(reloc_inode, 0, (u64)-1);
+		invalidate_mapping_pages(reloc_inode->i_mapping, 0, -1);
+		WARN_ON(reloc_inode->i_mapping->nrpages);
+	}
 
 	if (total_found > 0) {
-		printk("btrfs relocate found %llu last extent was %llu\n",
-		       (unsigned long long)total_found,
-		       (unsigned long long)found_key.objectid);
-		mutex_unlock(&root->fs_info->alloc_mutex);
-		trans = btrfs_start_transaction(tree_root, 1);
-		btrfs_commit_transaction(trans, tree_root);
-
-		btrfs_clean_old_snapshots(tree_root);
-
-		btrfs_start_delalloc_inodes(root);
-		btrfs_wait_ordered_extents(tree_root, 0);
-
-		trans = btrfs_start_transaction(tree_root, 1);
-		btrfs_commit_transaction(trans, tree_root);
-		mutex_lock(&root->fs_info->alloc_mutex);
+		printk("btrfs found %llu extents in pass %d\n",
+		       (unsigned long long)total_found, pass);
+		pass++;
 		goto again;
 	}
 
-	/*
-	 * we've freed all the extents, now remove the block
-	 * group item from the tree
-	 */
-	mutex_unlock(&root->fs_info->alloc_mutex);
+	/* delete reloc_inode */
+	iput(reloc_inode);
 
-	trans = btrfs_start_transaction(root, 1);
-
-	mutex_lock(&root->fs_info->alloc_mutex);
-	memcpy(&key, &shrink_block_group->key, sizeof(key));
-
-	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
-	if (ret > 0)
-		ret = -EIO;
-	if (ret < 0) {
-		btrfs_end_transaction(trans, root);
-		goto out;
-	}
-
-	spin_lock(&root->fs_info->block_group_cache_lock);
-	rb_erase(&shrink_block_group->cache_node,
-		 &root->fs_info->block_group_cache_tree);
-	spin_unlock(&root->fs_info->block_group_cache_lock);
-
-	ret = btrfs_remove_free_space(shrink_block_group, key.objectid,
-				      key.offset);
-	if (ret) {
-		btrfs_end_transaction(trans, root);
-		goto out;
-	}
-	/*
-	memset(shrink_block_group, 0, sizeof(*shrink_block_group));
-	kfree(shrink_block_group);
-	*/
-
-	btrfs_del_item(trans, root, path);
-	btrfs_release_path(root, path);
-	mutex_unlock(&root->fs_info->alloc_mutex);
-	btrfs_commit_transaction(trans, root);
+	/* unpin extents in this range */
+	trans = btrfs_start_transaction(info->tree_root, 1);
+	btrfs_commit_transaction(trans, info->tree_root);
 
 	mutex_lock(&root->fs_info->alloc_mutex);
 
-	/* the code to unpin extents might set a few bits in the free
-	 * space cache for this range again
-	 */
-	/* XXX? */
-	ret = btrfs_remove_free_space(shrink_block_group, key.objectid,
-				      key.offset);
+	spin_lock(&block_group->lock);
+	WARN_ON(block_group->pinned > 0);
+	WARN_ON(block_group->reserved > 0);
+	WARN_ON(btrfs_block_group_used(&block_group->item) > 0);
+	spin_unlock(&block_group->lock);
+	ret = 0;
 out:
-	btrfs_free_path(path);
 	mutex_unlock(&root->fs_info->alloc_mutex);
+	btrfs_free_path(path);
 	return ret;
 }
 
@@ -3922,6 +5054,33 @@
 	return ret;
 }
 
+int btrfs_free_block_groups(struct btrfs_fs_info *info)
+{
+	struct btrfs_block_group_cache *block_group;
+	struct rb_node *n;
+
+	mutex_lock(&info->alloc_mutex);
+	spin_lock(&info->block_group_cache_lock);
+	while ((n = rb_last(&info->block_group_cache_tree)) != NULL) {
+		block_group = rb_entry(n, struct btrfs_block_group_cache,
+				       cache_node);
+
+		spin_unlock(&info->block_group_cache_lock);
+		btrfs_remove_free_space_cache(block_group);
+		spin_lock(&info->block_group_cache_lock);
+
+		rb_erase(&block_group->cache_node,
+			 &info->block_group_cache_tree);
+		spin_lock(&block_group->space_info->lock);
+		list_del(&block_group->list);
+		spin_unlock(&block_group->space_info->lock);
+		kfree(block_group);
+	}
+	spin_unlock(&info->block_group_cache_lock);
+	mutex_unlock(&info->alloc_mutex);
+	return 0;
+}
+
 int btrfs_read_block_groups(struct btrfs_root *root)
 {
 	struct btrfs_path *path;
@@ -4039,3 +5198,46 @@
 
 	return 0;
 }
+
+int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
+			     struct btrfs_root *root, u64 group_start)
+{
+	struct btrfs_path *path;
+	struct btrfs_block_group_cache *block_group;
+	struct btrfs_key key;
+	int ret;
+
+	BUG_ON(!mutex_is_locked(&root->fs_info->alloc_mutex));
+	root = root->fs_info->extent_root;
+
+	block_group = btrfs_lookup_block_group(root->fs_info, group_start);
+	BUG_ON(!block_group);
+
+	memcpy(&key, &block_group->key, sizeof(key));
+
+	path = btrfs_alloc_path();
+	BUG_ON(!path);
+
+	btrfs_remove_free_space_cache(block_group);
+	rb_erase(&block_group->cache_node,
+		 &root->fs_info->block_group_cache_tree);
+	spin_lock(&block_group->space_info->lock);
+	list_del(&block_group->list);
+	spin_unlock(&block_group->space_info->lock);
+
+	/*
+	memset(shrink_block_group, 0, sizeof(*shrink_block_group));
+	kfree(shrink_block_group);
+	*/
+
+	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret > 0)
+		ret = -EIO;
+	if (ret < 0)
+		goto out;
+
+	ret = btrfs_del_item(trans, root, path);
+out:
+	btrfs_free_path(path);
+	return ret;
+}