Btrfs: Add a leaf reference cache

Much of the IO done while dropping snapshots is done looking up
leaves in the filesystem trees to see if they point to any extents and
to drop the references on any extents found.

This creates a cache so that IO isn't required.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/Makefile

@@ -6,7 +6,8 @@ btrfs-y := super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   hash.o file-item.o inode-item.o inode-map.o disk-io.o \
 	   transaction.o bit-radix.o inode.o file.o tree-defrag.o \
 	   extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \
-	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o
+	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
+	   ref-cache.o
 
 btrfs-$(CONFIG_FS_POSIX_ACL)	+= acl.o
 else

fs/btrfs/ctree.c

@@ -165,7 +165,7 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
 	btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN);
 
 	WARN_ON(btrfs_header_generation(buf) > trans->transid);
-	ret = btrfs_inc_ref(trans, new_root, buf);
+	ret = btrfs_inc_ref(trans, new_root, buf, 0);
 	kfree(new_root);
 
 	if (ret)
@@ -232,7 +232,7 @@ int __btrfs_cow_block(struct btrfs_trans_handle *trans,
 	WARN_ON(btrfs_header_generation(buf) > trans->transid);
 	if (btrfs_header_generation(buf) != trans->transid) {
 		different_trans = 1;
-		ret = btrfs_inc_ref(trans, root, buf);
+		ret = btrfs_inc_ref(trans, root, buf, 1);
 		if (ret)
 			return ret;
 	} else {

fs/btrfs/ctree.h

@@ -592,6 +592,10 @@ struct btrfs_fs_info {
 	u64 last_alloc;
 	u64 last_data_alloc;
 
+	spinlock_t ref_cache_lock;
+	u64 total_ref_cache_size;
+	u64 running_ref_cache_size;
+
 	u64 avail_data_alloc_bits;
 	u64 avail_metadata_alloc_bits;
 	u64 avail_system_alloc_bits;
@@ -613,6 +617,8 @@ struct btrfs_root {
 	spinlock_t node_lock;
 
 	struct extent_buffer *commit_root;
+	struct btrfs_leaf_ref_tree *ref_tree;
+
 	struct btrfs_root_item root_item;
 	struct btrfs_key root_key;
 	struct btrfs_fs_info *fs_info;
@@ -1430,7 +1436,7 @@ int btrfs_reserve_extent(struct btrfs_trans_handle *trans,
 				  u64 search_end, struct btrfs_key *ins,
 				  u64 data);
 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
-		  struct extent_buffer *buf);
+		  struct extent_buffer *buf, int cache_ref);
 int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 		      *root, u64 bytenr, u64 num_bytes,
 		      u64 root_objectid, u64 ref_generation,

fs/btrfs/disk-io.c

@@ -716,6 +716,7 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
 	root->node = NULL;
 	root->inode = NULL;
 	root->commit_root = NULL;
+	root->ref_tree = NULL;
 	root->sectorsize = sectorsize;
 	root->nodesize = nodesize;
 	root->leafsize = leafsize;
@@ -1165,12 +1166,19 @@ static int transaction_kthread(void *arg)
 		vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
 		mutex_lock(&root->fs_info->transaction_kthread_mutex);
 
+		printk("btrfs: total reference cache size %Lu\n",
+			root->fs_info->total_ref_cache_size);
+
 		mutex_lock(&root->fs_info->trans_mutex);
 		cur = root->fs_info->running_transaction;
 		if (!cur) {
 			mutex_unlock(&root->fs_info->trans_mutex);
 			goto sleep;
 		}
+
+		printk("btrfs: running reference cache size %Lu\n",
+			root->fs_info->running_ref_cache_size);
+
 		now = get_seconds();
 		if (now < cur->start_time || now - cur->start_time < 30) {
 			mutex_unlock(&root->fs_info->trans_mutex);
@@ -1233,6 +1241,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 	spin_lock_init(&fs_info->hash_lock);
 	spin_lock_init(&fs_info->delalloc_lock);
 	spin_lock_init(&fs_info->new_trans_lock);
+	spin_lock_init(&fs_info->ref_cache_lock);
 
 	init_completion(&fs_info->kobj_unregister);
 	fs_info->tree_root = tree_root;
@@ -1699,6 +1708,11 @@ int close_ctree(struct btrfs_root *root)
 		printk("btrfs: at unmount delalloc count %Lu\n",
 		       fs_info->delalloc_bytes);
 	}
+	if (fs_info->total_ref_cache_size) {
+		printk("btrfs: at umount reference cache size %Lu\n",
+			fs_info->total_ref_cache_size);
+	}
+	
 	if (fs_info->extent_root->node)
 		free_extent_buffer(fs_info->extent_root->node);
 

fs/btrfs/extent-tree.c

@@ -26,6 +26,7 @@
 #include "transaction.h"
 #include "volumes.h"
 #include "locking.h"
+#include "ref-cache.h"
 
 #define BLOCK_GROUP_DATA     EXTENT_WRITEBACK
 #define BLOCK_GROUP_METADATA EXTENT_UPTODATE
@@ -927,7 +928,7 @@ u32 btrfs_count_snapshots_in_path(struct btrfs_root *root,
 }
 
 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
-		  struct extent_buffer *buf)
+		  struct extent_buffer *buf, int cache_ref)
 {
 	u64 bytenr;
 	u32 nritems;
@@ -937,6 +938,7 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 	int level;
 	int ret;
 	int faili;
+	int nr_file_extents = 0;
 
 	if (!root->ref_cows)
 		return 0;
@@ -959,6 +961,9 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 			if (disk_bytenr == 0)
 				continue;
 
+			if (buf != root->commit_root)
+				nr_file_extents++;
+
 			mutex_lock(&root->fs_info->alloc_mutex);
 			ret = __btrfs_inc_extent_ref(trans, root, disk_bytenr,
 				    btrfs_file_extent_disk_num_bytes(buf, fi),
@@ -988,6 +993,53 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 			}
 		}
 	}
+	/* cache orignal leaf block's references */
+	if (level == 0 && cache_ref && buf != root->commit_root) {
+		struct btrfs_leaf_ref *ref;
+		struct btrfs_extent_info *info;
+
+		ref = btrfs_alloc_leaf_ref(nr_file_extents);
+		if (!ref) {
+			WARN_ON(1);
+			goto out;
+		}
+
+		btrfs_item_key_to_cpu(buf, &ref->key, 0);
+
+		ref->bytenr = buf->start;
+		ref->owner = btrfs_header_owner(buf);
+		ref->generation = btrfs_header_generation(buf);
+		ref->nritems = nr_file_extents;
+		info = ref->extents;
+		
+		for (i = 0; nr_file_extents > 0 && i < nritems; i++) {
+			u64 disk_bytenr;
+			btrfs_item_key_to_cpu(buf, &key, i);
+			if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
+				continue;
+			fi = btrfs_item_ptr(buf, i,
+					    struct btrfs_file_extent_item);
+			if (btrfs_file_extent_type(buf, fi) ==
+			    BTRFS_FILE_EXTENT_INLINE)
+				continue;
+			disk_bytenr = btrfs_file_extent_disk_bytenr(buf, fi);
+			if (disk_bytenr == 0)
+				continue;
+
+			info->bytenr = disk_bytenr;
+			info->num_bytes =
+				btrfs_file_extent_disk_num_bytes(buf, fi);
+			info->objectid = key.objectid;
+			info->offset = key.offset;
+			info++;
+		}
+
+		BUG_ON(!root->ref_tree);
+		ret = btrfs_add_leaf_ref(root, ref);
+		WARN_ON(ret);
+		btrfs_free_leaf_ref(ref);
+	}
+out:
 	return 0;
 fail:
 	WARN_ON(1);
@@ -2215,7 +2267,7 @@ struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 	return buf;
 }
 
-static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
+static int noinline drop_leaf_ref_no_cache(struct btrfs_trans_handle *trans,
 				  	   struct btrfs_root *root,
 					   struct extent_buffer *leaf)
 {
@@ -2266,6 +2318,30 @@ static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
+static int noinline drop_leaf_ref(struct btrfs_trans_handle *trans,
+				  	 struct btrfs_root *root,
+					 struct btrfs_leaf_ref *ref)
+{
+	int i;
+	int ret;
+	struct btrfs_extent_info *info = ref->extents;
+
+	mutex_unlock(&root->fs_info->alloc_mutex);
+	for (i = 0; i < ref->nritems; i++) {
+		mutex_lock(&root->fs_info->alloc_mutex);
+		ret = __btrfs_free_extent(trans, root,
+					info->bytenr, info->num_bytes,
+					ref->owner, ref->generation,
+					info->objectid, info->offset, 0);
+		mutex_unlock(&root->fs_info->alloc_mutex);
+		BUG_ON(ret);
+		info++;
+	}
+	mutex_lock(&root->fs_info->alloc_mutex);
+
+	return 0;
+}
+
 static void noinline reada_walk_down(struct btrfs_root *root,
 				     struct extent_buffer *node,
 				     int slot)
@@ -2341,6 +2417,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
 	struct extent_buffer *next;
 	struct extent_buffer *cur;
 	struct extent_buffer *parent;
+	struct btrfs_leaf_ref *ref;
 	u32 blocksize;
 	int ret;
 	u32 refs;
@@ -2370,7 +2447,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
 		    btrfs_header_nritems(cur))
 			break;
 		if (*level == 0) {
-			ret = drop_leaf_ref(trans, root, cur);
+			ret = drop_leaf_ref_no_cache(trans, root, cur);
 			BUG_ON(ret);
 			break;
 		}
@@ -2391,6 +2468,21 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
 			BUG_ON(ret);
 			continue;
 		}
+		
+		if (*level == 1) {
+			struct btrfs_key key;
+			btrfs_node_key_to_cpu(cur, &key, path->slots[*level]);
+			ref = btrfs_lookup_leaf_ref(root, &key);
+			if (ref) {
+				ret = drop_leaf_ref(trans, root, ref);
+				BUG_ON(ret);
+				btrfs_remove_leaf_ref(root, ref);
+				btrfs_free_leaf_ref(ref);
+				*level = 0;
+				break;
+			}
+		}
+
 		next = btrfs_find_tree_block(root, bytenr, blocksize);
 		if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
 			free_extent_buffer(next);
@@ -2398,7 +2490,6 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
 
 			if (path->slots[*level] == 0)
 				reada_walk_down(root, cur, path->slots[*level]);
-
 			next = read_tree_block(root, bytenr, blocksize,
 					       ptr_gen);
 			cond_resched();
@@ -2435,16 +2526,18 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
 	WARN_ON(*level >= BTRFS_MAX_LEVEL);
 
 	if (path->nodes[*level] == root->node) {
-		root_owner = root->root_key.objectid;
 		parent = path->nodes[*level];
+		bytenr = path->nodes[*level]->start;
 	} else {
 		parent = path->nodes[*level + 1];
-		root_owner = btrfs_header_owner(parent);
+		bytenr = btrfs_node_blockptr(parent, path->slots[*level + 1]);
 	}
 
+	blocksize = btrfs_level_size(root, *level);
+	root_owner = btrfs_header_owner(parent);
 	root_gen = btrfs_header_generation(parent);
-	ret = __btrfs_free_extent(trans, root, path->nodes[*level]->start,
-				path->nodes[*level]->len,
+
+	ret = __btrfs_free_extent(trans, root, bytenr, blocksize,
 				  root_owner, root_gen, 0, 0, 1);
 	free_extent_buffer(path->nodes[*level]);
 	path->nodes[*level] = NULL;

fs/btrfs/ref-cache.c

+/*
+ * Copyright (C) 2008 Oracle.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/sched.h>
+#include "ctree.h"
+#include "ref-cache.h"
+#include "transaction.h"
+
+struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents)
+{
+	struct btrfs_leaf_ref *ref;
+
+	ref = kmalloc(btrfs_leaf_ref_size(nr_extents), GFP_NOFS);
+	if (ref) {
+		memset(ref, 0, sizeof(*ref));
+		atomic_set(&ref->usage, 1);
+	}
+	return ref;
+}
+
+void btrfs_free_leaf_ref(struct btrfs_leaf_ref *ref)
+{
+	if (!ref)
+		return;
+	WARN_ON(atomic_read(&ref->usage) == 0);
+	if (atomic_dec_and_test(&ref->usage)) {
+		BUG_ON(ref->in_tree);
+		kfree(ref);
+	}
+}
+
+static int comp_keys(struct btrfs_key *k1, struct btrfs_key *k2)
+{
+	if (k1->objectid > k2->objectid)
+		return 1;
+	if (k1->objectid < k2->objectid)
+		return -1;
+	if (k1->type > k2->type)
+		return 1;
+	if (k1->type < k2->type)
+		return -1;
+	if (k1->offset > k2->offset)
+		return 1;
+	if (k1->offset < k2->offset)
+		return -1;
+	return 0;
+}
+
+static struct rb_node *tree_insert(struct rb_root *root, struct btrfs_key *key,
+				   struct rb_node *node)
+{
+	struct rb_node ** p = &root->rb_node;
+	struct rb_node * parent = NULL;
+	struct btrfs_leaf_ref *entry;
+	int ret;
+
+	while(*p) {
+		parent = *p;
+		entry = rb_entry(parent, struct btrfs_leaf_ref, rb_node);
+		WARN_ON(!entry->in_tree);
+
+		ret = comp_keys(key, &entry->key);
+		if (ret < 0)
+			p = &(*p)->rb_left;
+		else if (ret > 0)
+			p = &(*p)->rb_right;
+		else
+			return parent;
+	}
+	
+	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;
+}
+
+static struct rb_node *tree_search(struct rb_root *root, struct btrfs_key *key)
+{
+	struct rb_node * n = root->rb_node;
+	struct btrfs_leaf_ref *entry;
+	int ret;
+
+	while(n) {
+		entry = rb_entry(n, struct btrfs_leaf_ref, rb_node);
+		WARN_ON(!entry->in_tree);
+
+		ret = comp_keys(key, &entry->key);
+		if (ret < 0)
+			n = n->rb_left;
+		else if (ret > 0)
+			n = n->rb_right;
+		else
+			return n;
+	}
+	return NULL;
+}
+
+int btrfs_remove_leaf_refs(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 0;
+
+	spin_lock(&tree->lock);
+	while(!btrfs_leaf_ref_tree_empty(tree)) {
+		tree->last = NULL;
+		rb = rb_first(&tree->root);
+		ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
+		rb_erase(&ref->rb_node, &tree->root);
+		ref->in_tree = 0;
+
+		spin_unlock(&tree->lock);
+
+		btrfs_free_leaf_ref(ref);
+
+		cond_resched();
+		spin_lock(&tree->lock);
+	}
+	spin_unlock(&tree->lock);
+	return 0;
+}
+
+struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
+					     struct btrfs_key *key)
+{
+	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);
+	if (tree->last && comp_keys(key, &tree->last->key) == 0) {
+		ref = tree->last;
+	} else {
+		rb = tree_search(&tree->root, key);
+		if (rb) {
+			ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
+			tree->last = ref;
+		}
+	}
+	if (ref)
+		atomic_inc(&ref->usage);
+	spin_unlock(&tree->lock);
+	return ref;
+}
+
+int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
+{
+	int ret = 0;
+	struct rb_node *rb;
+	size_t size = btrfs_leaf_ref_size(ref->nritems);
+	struct btrfs_leaf_ref_tree *tree = root->ref_tree;
+	struct btrfs_transaction *trans = root->fs_info->running_transaction;
+
+	spin_lock(&tree->lock);
+	rb = tree_insert(&tree->root, &ref->key, &ref->rb_node);
+	if (rb) {
+		ret = -EEXIST;
+	} else {
+		spin_lock(&root->fs_info->ref_cache_lock);
+		root->fs_info->total_ref_cache_size += size;
+		if (trans && tree->generation == trans->transid)
+			root->fs_info->running_ref_cache_size += size;
+		spin_unlock(&root->fs_info->ref_cache_lock);
+
+		tree->last = ref;
+		atomic_inc(&ref->usage);
+	}
+	spin_unlock(&tree->lock);
+	return ret;
+}
+
+int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
+{
+	size_t size = btrfs_leaf_ref_size(ref->nritems);
+	struct btrfs_leaf_ref_tree *tree = root->ref_tree;
+	struct btrfs_transaction *trans = root->fs_info->running_transaction;
+
+	BUG_ON(!ref->in_tree);
+	spin_lock(&tree->lock);
+	
+	spin_lock(&root->fs_info->ref_cache_lock);
+	root->fs_info->total_ref_cache_size -= size;
+	if (trans && tree->generation == trans->transid)
+		root->fs_info->running_ref_cache_size -= size;
+	spin_unlock(&root->fs_info->ref_cache_lock);
+
+	if (tree->last == ref) {
+		struct rb_node *next = rb_next(&ref->rb_node);
+		if (next) {
+			tree->last = rb_entry(next, struct btrfs_leaf_ref,
+					      rb_node);
+		} else
+			tree->last = NULL;
+	}
+
+	rb_erase(&ref->rb_node, &tree->root);
+	ref->in_tree = 0;
+
+	spin_unlock(&tree->lock);
+
+	btrfs_free_leaf_ref(ref);
+	return 0;
+}
+

fs/btrfs/ref-cache.h

+/*
+ * Copyright (C) 2008 Oracle.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+struct btrfs_extent_info {
+	u64 bytenr;
+	u64 num_bytes;
+	u64 objectid;
+	u64 offset;
+};
+
+struct btrfs_leaf_ref {
+	struct rb_node rb_node;
+	struct btrfs_key key;
+	int in_tree;
+	atomic_t usage;
+
+	u64 bytenr;
+	u64 owner;
+	u64 generation;
+	int nritems;
+	struct btrfs_extent_info extents[];
+};
+
+struct btrfs_leaf_ref_tree {
+	struct rb_root root;
+	struct btrfs_leaf_ref *last;
+	u64 generation;
+	spinlock_t lock;
+};
+
+static inline size_t btrfs_leaf_ref_size(int nr_extents)
+{
+	return sizeof(struct btrfs_leaf_ref) + 
+	       sizeof(struct btrfs_extent_info) * nr_extents;
+}
+
+static inline void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree)
+{
+	tree->root.rb_node = NULL;
+	tree->last = NULL;
+	tree->generation = 0;
+	spin_lock_init(&tree->lock);
+}
+
+static inline int btrfs_leaf_ref_tree_empty(struct btrfs_leaf_ref_tree *tree)
+{
+	return RB_EMPTY_ROOT(&tree->root);
+}
+
+void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree);
+struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents);
+void btrfs_free_leaf_ref(struct btrfs_leaf_ref *ref);
+struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
+					     struct btrfs_key *key);
+int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
+int btrfs_remove_leaf_refs(struct btrfs_root *root);
+int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);

fs/btrfs/transaction.c

@@ -24,6 +24,7 @@
 #include "disk-io.h"
 #include "transaction.h"
 #include "locking.h"
+#include "ref-cache.h"
 
 static int total_trans = 0;
 extern struct kmem_cache *btrfs_trans_handle_cachep;
@@ -31,6 +32,13 @@ extern struct kmem_cache *btrfs_transaction_cachep;
 
 #define BTRFS_ROOT_TRANS_TAG 0
 
+struct dirty_root {
+	struct list_head list;
+	struct btrfs_root *root;
+	struct btrfs_root *latest_root;
+	struct btrfs_leaf_ref_tree ref_tree;
+};
+
 static noinline void put_transaction(struct btrfs_transaction *transaction)
 {
 	WARN_ON(transaction->use_count == 0);
@@ -84,6 +92,7 @@ static noinline int join_transaction(struct btrfs_root *root)
 
 static noinline int record_root_in_trans(struct btrfs_root *root)
 {
+	struct dirty_root *dirty;
 	u64 running_trans_id = root->fs_info->running_transaction->transid;
 	if (root->ref_cows && root->last_trans < running_trans_id) {
 		WARN_ON(root == root->fs_info->extent_root);
@@ -91,7 +100,25 @@ static noinline int record_root_in_trans(struct btrfs_root *root)
 			radix_tree_tag_set(&root->fs_info->fs_roots_radix,
 				   (unsigned long)root->root_key.objectid,
 				   BTRFS_ROOT_TRANS_TAG);
+
+			dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
+			BUG_ON(!dirty);
+			dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
+			BUG_ON(!dirty->root);
+
+			dirty->latest_root = root;
+			INIT_LIST_HEAD(&dirty->list);
+			btrfs_leaf_ref_tree_init(&dirty->ref_tree);
+			dirty->ref_tree.generation = running_trans_id;
+
 			root->commit_root = btrfs_root_node(root);
+			root->ref_tree = &dirty->ref_tree;
+
+			memcpy(dirty->root, root, sizeof(*root));
+			spin_lock_init(&dirty->root->node_lock);
+			mutex_init(&dirty->root->objectid_mutex);
+			dirty->root->node = root->commit_root;
+			dirty->root->commit_root = NULL;
 		} else {
 			WARN_ON(1);
 		}
@@ -310,12 +337,6 @@ int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
-struct dirty_root {
-	struct list_head list;
-	struct btrfs_root *root;
-	struct btrfs_root *latest_root;
-};
-
 int btrfs_add_dead_root(struct btrfs_root *root,
 			struct btrfs_root *latest,
 			struct list_head *dead_list)
@@ -325,8 +346,10 @@ int btrfs_add_dead_root(struct btrfs_root *root,
 	dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 	if (!dirty)
 		return -ENOMEM;
+	btrfs_leaf_ref_tree_init(&dirty->ref_tree);
 	dirty->root = root;
 	dirty->latest_root = latest;
+	root->ref_tree = NULL;
 	list_add(&dirty->list, dead_list);
 	return 0;
 }
@@ -354,11 +377,23 @@ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 			radix_tree_tag_clear(radix,
 				     (unsigned long)root->root_key.objectid,
 				     BTRFS_ROOT_TRANS_TAG);
+
+			BUG_ON(!root->ref_tree);
+			dirty = container_of(root->ref_tree, struct dirty_root,
+					     ref_tree);
+
 			if (root->commit_root == root->node) {
 				WARN_ON(root->node->start !=
 					btrfs_root_bytenr(&root->root_item));
+
+				BUG_ON(!btrfs_leaf_ref_tree_empty(
+							root->ref_tree));
 				free_extent_buffer(root->commit_root);
 				root->commit_root = NULL;
+				root->ref_tree = NULL;
+				
+				kfree(dirty->root);
+				kfree(dirty);
 
 				/* make sure to update the root on disk
 				 * so we get any updates to the block used
@@ -370,23 +405,12 @@ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 						&root->root_item);
 				continue;
 			}
-			dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
-			BUG_ON(!dirty);
-			dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
-			BUG_ON(!dirty->root);
 
 			memset(&root->root_item.drop_progress, 0,
 			       sizeof(struct btrfs_disk_key));
 			root->root_item.drop_level = 0;
-
-			memcpy(dirty->root, root, sizeof(*root));
-			dirty->root->node = root->commit_root;
-			dirty->latest_root = root;
-			spin_lock_init(&dirty->root->node_lock);
-			mutex_init(&dirty->root->objectid_mutex);
-
 			root->commit_root = NULL;
-
+			root->ref_tree = NULL;
 			root->root_key.offset = root->fs_info->generation;
 			btrfs_set_root_bytenr(&root->root_item,
 					      root->node->start);
@@ -409,6 +433,7 @@ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 				list_add(&dirty->list, list);
 			} else {
 				WARN_ON(1);
+				free_extent_buffer(dirty->root->node);
 				kfree(dirty->root);
 				kfree(dirty);
 			}
@@ -514,6 +539,8 @@ static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
 		ret = btrfs_end_transaction(trans, tree_root);
 		BUG_ON(ret);
 
+		btrfs_remove_leaf_refs(dirty->root);
+
 		free_extent_buffer(dirty->root->node);
 		kfree(dirty->root);
 		kfree(dirty);
@@ -698,6 +725,10 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 			      &dirty_fs_roots);
 	BUG_ON(ret);
 
+	spin_lock(&root->fs_info->ref_cache_lock);
+	root->fs_info->running_ref_cache_size = 0;
+	spin_unlock(&root->fs_info->ref_cache_lock);
+
 	ret = btrfs_commit_tree_roots(trans, root);
 	BUG_ON(ret);