10 files changed, 1066 insertions, 722 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 6f467901246f..50aea8cb653a 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -125,7 +125,6 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
 	u32 nritems;
 	int ret = 0;
 	int level;
-	struct btrfs_key first_key;
 	struct btrfs_root *new_root;
 
 	new_root = kmalloc(sizeof(*new_root), GFP_NOFS);
@@ -141,18 +140,10 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
 
 	level = btrfs_header_level(buf);
 	nritems = btrfs_header_nritems(buf);
-	if (nritems) {
-		if (level == 0)
-			btrfs_item_key_to_cpu(buf, &first_key, 0);
-		else
-			btrfs_node_key_to_cpu(buf, &first_key, 0);
-	} else {
-		first_key.objectid = 0;
-	}
-	cow = btrfs_alloc_free_block(trans, new_root, buf->len,
-				       new_root_objectid,
-				       trans->transid, first_key.objectid,
-				       level, buf->start, 0);
+
+	cow = btrfs_alloc_free_block(trans, new_root, buf->len, 0,
+				     new_root_objectid, trans->transid,
+				     level, buf->start, 0);
 	if (IS_ERR(cow)) {
 		kfree(new_root);
 		return PTR_ERR(cow);
@@ -165,7 +156,7 @@ 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, 0);
+	ret = btrfs_inc_ref(trans, new_root, buf, cow, NULL);
 	kfree(new_root);
 
 	if (ret)
@@ -184,39 +175,31 @@ int noinline __btrfs_cow_block(struct btrfs_trans_handle *trans,
 			     u64 search_start, u64 empty_size,
 			     u64 prealloc_dest)
 {
-	u64 root_gen;
+	u64 parent_start;
 	struct extent_buffer *cow;
 	u32 nritems;
 	int ret = 0;
 	int different_trans = 0;
 	int level;
 	int unlock_orig = 0;
-	struct btrfs_key first_key;
 
 	if (*cow_ret == buf)
 		unlock_orig = 1;
 
 	WARN_ON(!btrfs_tree_locked(buf));
 
-	if (root->ref_cows) {
-		root_gen = trans->transid;
-	} else {
-		root_gen = 0;
-	}
+	if (parent)
+		parent_start = parent->start;
+	else
+		parent_start = 0;
+
 	WARN_ON(root->ref_cows && trans->transid !=
 		root->fs_info->running_transaction->transid);
 	WARN_ON(root->ref_cows && trans->transid != root->last_trans);
 
 	level = btrfs_header_level(buf);
 	nritems = btrfs_header_nritems(buf);
-	if (nritems) {
-		if (level == 0)
-			btrfs_item_key_to_cpu(buf, &first_key, 0);
-		else
-			btrfs_node_key_to_cpu(buf, &first_key, 0);
-	} else {
-		first_key.objectid = 0;
-	}
+
 	if (prealloc_dest) {
 		struct btrfs_key ins;
 
@@ -224,19 +207,19 @@ int noinline __btrfs_cow_block(struct btrfs_trans_handle *trans,
 		ins.offset = buf->len;
 		ins.type = BTRFS_EXTENT_ITEM_KEY;
 
-		ret = btrfs_alloc_reserved_extent(trans, root,
+		ret = btrfs_alloc_reserved_extent(trans, root, parent_start,
 						  root->root_key.objectid,
-						  root_gen, level,
-						  first_key.objectid,
+						  trans->transid, level, 0,
 						  &ins);
 		BUG_ON(ret);
 		cow = btrfs_init_new_buffer(trans, root, prealloc_dest,
 					    buf->len);
 	} else {
 		cow = btrfs_alloc_free_block(trans, root, buf->len,
+					     parent_start,
 					     root->root_key.objectid,
-					     root_gen, first_key.objectid,
-					     level, search_start, empty_size);
+					     trans->transid, level,
+					     search_start, empty_size);
 	}
 	if (IS_ERR(cow))
 		return PTR_ERR(cow);
@@ -249,17 +232,23 @@ int noinline __btrfs_cow_block(struct btrfs_trans_handle *trans,
 
 	WARN_ON(btrfs_header_generation(buf) > trans->transid);
 	if (btrfs_header_generation(buf) != trans->transid) {
+		u32 nr_extents;
 		different_trans = 1;
-		ret = btrfs_inc_ref(trans, root, buf, 1);
+		ret = btrfs_inc_ref(trans, root, buf, cow, &nr_extents);
 		if (ret)
 			return ret;
+
+		ret = btrfs_cache_ref(trans, root, buf, nr_extents);
+		WARN_ON(ret);
 	} else {
+		ret = btrfs_update_ref(trans, root, buf, cow, 0, nritems);
+		if (ret)
+			return ret;
 		clean_tree_block(trans, root, buf);
 	}
 
 	if (buf == root->node) {
 		WARN_ON(parent && parent != buf);
-		root_gen = btrfs_header_generation(buf);
 
 		spin_lock(&root->node_lock);
 		root->node = cow;
@@ -268,13 +257,14 @@ int noinline __btrfs_cow_block(struct btrfs_trans_handle *trans,
 
 		if (buf != root->commit_root) {
 			btrfs_free_extent(trans, root, buf->start,
-					  buf->len, root->root_key.objectid,
-					  root_gen, 0, 0, 1);
+					  buf->len, buf->start,
+					  root->root_key.objectid,
+					  btrfs_header_generation(buf),
+					  0, 0, 1);
 		}
 		free_extent_buffer(buf);
 		add_root_to_dirty_list(root);
 	} else {
-		root_gen = btrfs_header_generation(parent);
 		btrfs_set_node_blockptr(parent, parent_slot,
 					cow->start);
 		WARN_ON(trans->transid == 0);
@@ -283,8 +273,8 @@ int noinline __btrfs_cow_block(struct btrfs_trans_handle *trans,
 		btrfs_mark_buffer_dirty(parent);
 		WARN_ON(btrfs_header_generation(parent) != trans->transid);
 		btrfs_free_extent(trans, root, buf->start, buf->len,
-				  btrfs_header_owner(parent), root_gen,
-				  0, 0, 1);
+				  parent_start, btrfs_header_owner(parent),
+				  btrfs_header_generation(parent), 0, 0, 1);
 	}
 	if (unlock_orig)
 		btrfs_tree_unlock(buf);
@@ -831,6 +821,12 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 		root->node = child;
 		spin_unlock(&root->node_lock);
 
+		ret = btrfs_update_extent_ref(trans, root, child->start,
+					      mid->start, child->start,
+					      root->root_key.objectid,
+					      trans->transid, level - 1, 0);
+		BUG_ON(ret);
+
 		add_root_to_dirty_list(root);
 		btrfs_tree_unlock(child);
 		path->locks[level] = 0;
@@ -840,7 +836,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 		/* once for the path */
 		free_extent_buffer(mid);
 		ret = btrfs_free_extent(trans, root, mid->start, mid->len,
-					root->root_key.objectid,
+					mid->start, root->root_key.objectid,
 					btrfs_header_generation(mid), 0, 0, 1);
 		/* once for the root ptr */
 		free_extent_buffer(mid);
@@ -905,7 +901,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 			if (wret)
 				ret = wret;
 			wret = btrfs_free_extent(trans, root, bytenr,
-						 blocksize,
+						 blocksize, parent->start,
 						 btrfs_header_owner(parent),
 						 generation, 0, 0, 1);
 			if (wret)
@@ -954,6 +950,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 		if (wret)
 			ret = wret;
 		wret = btrfs_free_extent(trans, root, bytenr, blocksize,
+					 parent->start,
 					 btrfs_header_owner(parent),
 					 root_gen, 0, 0, 1);
 		if (wret)
@@ -1500,6 +1497,41 @@ static int fixup_low_keys(struct btrfs_trans_handle *trans,
 }
 
 /*
+ * update item key.
+ *
+ * This function isn't completely safe. It's the caller's responsibility
+ * that the new key won't break the order
+ */
+int btrfs_set_item_key_safe(struct btrfs_trans_handle *trans,
+			    struct btrfs_root *root, struct btrfs_path *path,
+			    struct btrfs_key *new_key)
+{
+	struct btrfs_disk_key disk_key;
+	struct extent_buffer *eb;
+	int slot;
+
+	eb = path->nodes[0];
+	slot = path->slots[0];
+	if (slot > 0) {
+		btrfs_item_key(eb, &disk_key, slot - 1);
+		if (comp_keys(&disk_key, new_key) >= 0)
+			return -1;
+	}
+	if (slot < btrfs_header_nritems(eb) - 1) {
+		btrfs_item_key(eb, &disk_key, slot + 1);
+		if (comp_keys(&disk_key, new_key) <= 0)
+			return -1;
+	}
+
+	btrfs_cpu_key_to_disk(&disk_key, new_key);
+	btrfs_set_item_key(eb, &disk_key, slot);
+	btrfs_mark_buffer_dirty(eb);
+	if (slot == 0)
+		fixup_low_keys(trans, root, path, &disk_key, 1);
+	return 0;
+}
+
+/*
  * try to push data from one node into the next node left in the
  * tree.
  *
@@ -1558,6 +1590,10 @@ static int push_node_left(struct btrfs_trans_handle *trans,
 	btrfs_set_header_nritems(dst, dst_nritems + push_items);
 	btrfs_mark_buffer_dirty(src);
 	btrfs_mark_buffer_dirty(dst);
+
+	ret = btrfs_update_ref(trans, root, src, dst, dst_nritems, push_items);
+	BUG_ON(ret);
+
 	return ret;
 }
 
@@ -1619,6 +1655,10 @@ static int balance_node_right(struct btrfs_trans_handle *trans,
 
 	btrfs_mark_buffer_dirty(src);
 	btrfs_mark_buffer_dirty(dst);
+
+	ret = btrfs_update_ref(trans, root, src, dst, 0, push_items);
+	BUG_ON(ret);
+
 	return ret;
 }
 
@@ -1633,30 +1673,24 @@ static int noinline insert_new_root(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root,
 			   struct btrfs_path *path, int level)
 {
-	u64 root_gen;
 	u64 lower_gen;
 	struct extent_buffer *lower;
 	struct extent_buffer *c;
 	struct extent_buffer *old;
 	struct btrfs_disk_key lower_key;
+	int ret;
 
 	BUG_ON(path->nodes[level]);
 	BUG_ON(path->nodes[level-1] != root->node);
 
-	if (root->ref_cows)
-		root_gen = trans->transid;
-	else
-		root_gen = 0;
-
 	lower = path->nodes[level-1];
 	if (level == 1)
 		btrfs_item_key(lower, &lower_key, 0);
 	else
 		btrfs_node_key(lower, &lower_key, 0);
 
-	c = btrfs_alloc_free_block(trans, root, root->nodesize,
-				   root->root_key.objectid,
-				   root_gen, le64_to_cpu(lower_key.objectid),
+	c = btrfs_alloc_free_block(trans, root, root->nodesize, 0,
+				   root->root_key.objectid, trans->transid,
 				   level, root->node->start, 0);
 	if (IS_ERR(c))
 		return PTR_ERR(c);
@@ -1679,7 +1713,7 @@ static int noinline insert_new_root(struct btrfs_trans_handle *trans,
 	btrfs_set_node_key(c, &lower_key, 0);
 	btrfs_set_node_blockptr(c, 0, lower->start);
 	lower_gen = btrfs_header_generation(lower);
-	WARN_ON(lower_gen == 0);
+	WARN_ON(lower_gen != trans->transid);
 
 	btrfs_set_node_ptr_generation(c, 0, lower_gen);
 
@@ -1690,6 +1724,12 @@ static int noinline insert_new_root(struct btrfs_trans_handle *trans,
 	root->node = c;
 	spin_unlock(&root->node_lock);
 
+	ret = btrfs_update_extent_ref(trans, root, lower->start,
+				      lower->start, c->start,
+				      root->root_key.objectid,
+				      trans->transid, level - 1, 0);
+	BUG_ON(ret);
+
 	/* the super has an extra ref to root->node */
 	free_extent_buffer(old);
 
@@ -1698,20 +1738,6 @@ static int noinline insert_new_root(struct btrfs_trans_handle *trans,
 	path->nodes[level] = c;
 	path->locks[level] = 1;
 	path->slots[level] = 0;
-
-	if (root->ref_cows && lower_gen != trans->transid) {
-		struct btrfs_path *back_path = btrfs_alloc_path();
-		int ret;
-		mutex_lock(&root->fs_info->alloc_mutex);
-		ret = btrfs_insert_extent_backref(trans,
-						  root->fs_info->extent_root,
-						  path, lower->start,
-						  root->root_key.objectid,
-						  trans->transid, 0, 0);
-		BUG_ON(ret);
-		mutex_unlock(&root->fs_info->alloc_mutex);
-		btrfs_free_path(back_path);
-	}
 	return 0;
 }
 
@@ -1766,7 +1792,6 @@ static noinline int split_node(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *root,
 			       struct btrfs_path *path, int level)
 {
-	u64 root_gen;
 	struct extent_buffer *c;
 	struct extent_buffer *split;
 	struct btrfs_disk_key disk_key;
@@ -1793,17 +1818,11 @@ static noinline int split_node(struct btrfs_trans_handle *trans,
 	}
 
 	c_nritems = btrfs_header_nritems(c);
-	if (root->ref_cows)
-		root_gen = trans->transid;
-	else
-		root_gen = 0;
 
-	btrfs_node_key(c, &disk_key, 0);
 	split = btrfs_alloc_free_block(trans, root, root->nodesize,
-					 root->root_key.objectid,
-					 root_gen,
-					 btrfs_disk_key_objectid(&disk_key),
-					 level, c->start, 0);
+					path->nodes[level + 1]->start,
+					root->root_key.objectid,
+					trans->transid, level, c->start, 0);
 	if (IS_ERR(split))
 		return PTR_ERR(split);
 
@@ -1840,6 +1859,9 @@ static noinline int split_node(struct btrfs_trans_handle *trans,
 	if (wret)
 		ret = wret;
 
+	ret = btrfs_update_ref(trans, root, c, split, 0, c_nritems - mid);
+	BUG_ON(ret);
+
 	if (path->slots[level] >= mid) {
 		path->slots[level] -= mid;
 		btrfs_tree_unlock(c);
@@ -1955,10 +1977,23 @@ static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
 	else
 		nr = 1;
 
+	if (path->slots[0] >= left_nritems)
+		push_space += data_size + sizeof(*item);
+
 	i = left_nritems - 1;
 	while (i >= nr) {
 		item = btrfs_item_nr(left, i);
 
+		if (!empty && push_items > 0) {
+			if (path->slots[0] > i)
+				break;
+			if (path->slots[0] == i) {
+				int space = btrfs_leaf_free_space(root, left);
+				if (space + push_space * 2 > free_space)
+					break;
+			}
+		}
+
 		if (path->slots[0] == i)
 			push_space += data_size + sizeof(*item);
 
@@ -1973,6 +2008,7 @@ static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
 		this_item_size = btrfs_item_size(left, item);
 		if (this_item_size + sizeof(*item) + push_space > free_space)
 			break;
+
 		push_items++;
 		push_space += this_item_size + sizeof(*item);
 		if (i == 0)
@@ -2046,6 +2082,9 @@ static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
 		btrfs_mark_buffer_dirty(left);
 	btrfs_mark_buffer_dirty(right);
 
+	ret = btrfs_update_ref(trans, root, left, right, 0, push_items);
+	BUG_ON(ret);
+
 	btrfs_item_key(right, &disk_key, 0);
 	btrfs_set_node_key(upper, &disk_key, slot + 1);
 	btrfs_mark_buffer_dirty(upper);
@@ -2147,6 +2186,16 @@ static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
 					KM_USER1);
 		}
 
+		if (!empty && push_items > 0) {
+			if (path->slots[0] < i)
+				break;
+			if (path->slots[0] == i) {
+				int space = btrfs_leaf_free_space(root, right);
+				if (space + push_space * 2 > free_space)
+					break;
+			}
+		}
+
 		if (path->slots[0] == i)
 			push_space += data_size + sizeof(*item);
 
@@ -2255,6 +2304,10 @@ static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
 	if (right_nritems)
 		btrfs_mark_buffer_dirty(right);
 
+	ret = btrfs_update_ref(trans, root, right, left,
+			       old_left_nritems, push_items);
+	BUG_ON(ret);
+
 	btrfs_item_key(right, &disk_key, 0);
 	wret = fixup_low_keys(trans, root, path, &disk_key, 1);
 	if (wret)
@@ -2294,7 +2347,6 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans,
 			       struct btrfs_path *path, int data_size,
 			       int extend)
 {
-	u64 root_gen;
 	struct extent_buffer *l;
 	u32 nritems;
 	int mid;
@@ -2313,11 +2365,6 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans,
 	if (extend)
 		space_needed = data_size;
 
-	if (root->ref_cows)
-		root_gen = trans->transid;
-	else
-		root_gen = 0;
-
 	/* first try to make some room by pushing left and right */
 	if (ins_key->type != BTRFS_DIR_ITEM_KEY) {
 		wret = push_leaf_right(trans, root, path, data_size, 0);
@@ -2348,13 +2395,10 @@ again:
 	nritems = btrfs_header_nritems(l);
 	mid = (nritems + 1)/ 2;
 
-	btrfs_item_key(l, &disk_key, 0);
-
 	right = btrfs_alloc_free_block(trans, root, root->leafsize,
-					 root->root_key.objectid,
-					 root_gen,
-					 le64_to_cpu(disk_key.objectid),
-					 0, l->start, 0);
+					path->nodes[1]->start,
+					root->root_key.objectid,
+					trans->transid, 0, l->start, 0);
 	if (IS_ERR(right)) {
 		BUG_ON(1);
 		return PTR_ERR(right);
@@ -2485,6 +2529,9 @@ again:
 	btrfs_mark_buffer_dirty(l);
 	BUG_ON(path->slots[0] != slot);
 
+	ret = btrfs_update_ref(trans, root, l, right, 0, nritems);
+	BUG_ON(ret);
+
 	if (mid <= slot) {
 		btrfs_tree_unlock(path->nodes[0]);
 		free_extent_buffer(path->nodes[0]);
@@ -2956,6 +3003,7 @@ int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 				ret = wret;
 			wret = btrfs_free_extent(trans, root,
 					 leaf->start, leaf->len,
+					 path->nodes[1]->start,
 					 btrfs_header_owner(path->nodes[1]),
 					 root_gen, 0, 0, 1);
 			if (wret)
@@ -3007,7 +3055,7 @@ int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 
 				free_extent_buffer(leaf);
 				wret = btrfs_free_extent(trans, root, bytenr,
-					     blocksize,
+					     blocksize, path->nodes[1]->start,
 					     btrfs_header_owner(path->nodes[1]),
 					     root_gen, 0, 0, 1);
 				if (wret)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 730aae3bc181..138c157bbc45 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -40,7 +40,7 @@ extern struct kmem_cache *btrfs_bit_radix_cachep;
 extern struct kmem_cache *btrfs_path_cachep;
 struct btrfs_ordered_sum;
 
-#define BTRFS_MAGIC "_B8RfS_M"
+#define BTRFS_MAGIC "_B9RfS_M"
 
 #define BTRFS_ACL_NOT_CACHED    ((void *)-1)
 
@@ -81,6 +81,9 @@ struct btrfs_ordered_sum;
 #define BTRFS_TREE_LOG_OBJECTID -6ULL
 #define BTRFS_TREE_LOG_FIXUP_OBJECTID -7ULL
 
+/* dummy objectid represents multiple objectids */
+#define BTRFS_MULTIPLE_OBJECTIDS -255ULL
+
 /*
  * All files have objectids in this range.
  */
@@ -369,6 +372,7 @@ struct btrfs_extent_ref {
 	__le64 generation;
 	__le64 objectid;
 	__le64 offset;
+	__le32 num_refs;
 } __attribute__ ((__packed__));
 
 /* dev extents record free space on individual devices.  The owner
@@ -1047,9 +1051,6 @@ btrfs_inode_otime(struct btrfs_inode_item *inode_item)
 BTRFS_SETGET_FUNCS(timespec_sec, struct btrfs_timespec, sec, 64);
 BTRFS_SETGET_FUNCS(timespec_nsec, struct btrfs_timespec, nsec, 32);
 
-/* struct btrfs_extent_item */
-BTRFS_SETGET_FUNCS(extent_refs, struct btrfs_extent_item, refs, 32);
-
 /* struct btrfs_dev_extent */
 BTRFS_SETGET_FUNCS(dev_extent_chunk_tree, struct btrfs_dev_extent,
 		   chunk_tree, 64);
@@ -1070,14 +1071,20 @@ BTRFS_SETGET_FUNCS(ref_root, struct btrfs_extent_ref, root, 64);
 BTRFS_SETGET_FUNCS(ref_generation, struct btrfs_extent_ref, generation, 64);
 BTRFS_SETGET_FUNCS(ref_objectid, struct btrfs_extent_ref, objectid, 64);
 BTRFS_SETGET_FUNCS(ref_offset, struct btrfs_extent_ref, offset, 64);
+BTRFS_SETGET_FUNCS(ref_num_refs, struct btrfs_extent_ref, num_refs, 32);
 
 BTRFS_SETGET_STACK_FUNCS(stack_ref_root, struct btrfs_extent_ref, root, 64);
 BTRFS_SETGET_STACK_FUNCS(stack_ref_generation, struct btrfs_extent_ref,
 			 generation, 64);
 BTRFS_SETGET_STACK_FUNCS(stack_ref_objectid, struct btrfs_extent_ref,
 			 objectid, 64);
-BTRFS_SETGET_STACK_FUNCS(stack_ref_offset, struct btrfs_extent_ref, offset, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_ref_offset, struct btrfs_extent_ref,
+			 offset, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_ref_num_refs, struct btrfs_extent_ref,
+			 num_refs, 32);
 
+/* struct btrfs_extent_item */
+BTRFS_SETGET_FUNCS(extent_refs, struct btrfs_extent_item, refs, 32);
 BTRFS_SETGET_STACK_FUNCS(stack_extent_refs, struct btrfs_extent_item,
 			 refs, 32);
 
@@ -1474,8 +1481,7 @@ static inline struct dentry *fdentry(struct file *file) {
 }
 
 /* extent-tree.c */
-int btrfs_lookup_extent(struct btrfs_root *root, struct btrfs_path *path,
-			u64 start, u64 len);
+int btrfs_lookup_extent(struct btrfs_root *root, u64 start, u64 len);
 int btrfs_update_pinned_extents(struct btrfs_root *root,
 				u64 bytenr, u64 num, int pin);
 int btrfs_drop_leaf_ref(struct btrfs_trans_handle *trans,
@@ -1495,10 +1501,9 @@ struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
 						 int data, int owner);
 struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 					     struct btrfs_root *root,
-					     u32 blocksize,
+					     u32 blocksize, u64 parent,
 					     u64 root_objectid,
 					     u64 ref_generation,
-					     u64 first_objectid,
 					     int level,
 					     u64 hint,
 					     u64 empty_size);
@@ -1508,23 +1513,24 @@ struct extent_buffer *btrfs_init_new_buffer(struct btrfs_trans_handle *trans,
 int btrfs_shrink_extent_tree(struct btrfs_root *root, u64 new_size);
 int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
 				 struct btrfs_root *root,
-				 struct btrfs_path *path, u64 bytenr,
+				 struct btrfs_path *path,
+				 u64 bytenr, u64 parent,
 				 u64 root_objectid, u64 ref_generation,
 				 u64 owner, u64 owner_offset);
 int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
 		       struct btrfs_root *root,
-		       u64 num_bytes, u64 min_bytes,
+		       u64 num_bytes, u64 parent, u64 min_bytes,
 		       u64 root_objectid, u64 ref_generation,
 		       u64 owner, u64 owner_offset,
 		       u64 empty_size, u64 hint_byte,
 		       u64 search_end, struct btrfs_key *ins, u64 data);
 int btrfs_alloc_reserved_extent(struct btrfs_trans_handle *trans,
-				struct btrfs_root *root,
+				struct btrfs_root *root, u64 parent,
 				u64 root_objectid, u64 ref_generation,
 				u64 owner, u64 owner_offset,
 				struct btrfs_key *ins);
 int btrfs_alloc_logged_extent(struct btrfs_trans_handle *trans,
-				struct btrfs_root *root,
+				struct btrfs_root *root, u64 parent,
 				u64 root_objectid, u64 ref_generation,
 				u64 owner, u64 owner_offset,
 				struct btrfs_key *ins);
@@ -1535,9 +1541,16 @@ 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, int cache_ref);
-int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
-		      *root, u64 bytenr, u64 num_bytes,
+		  struct extent_buffer *orig_buf, struct extent_buffer *buf,
+		  u32 *nr_extents);
+int btrfs_cache_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+		    struct extent_buffer *buf, u32 nr_extents);
+int btrfs_update_ref(struct btrfs_trans_handle *trans,
+		     struct btrfs_root *root, struct extent_buffer *orig_buf,
+		     struct extent_buffer *buf, int start_slot, int nr);
+int btrfs_free_extent(struct btrfs_trans_handle *trans,
+		      struct btrfs_root *root,
+		      u64 bytenr, u64 num_bytes, u64 parent,
 		      u64 root_objectid, u64 ref_generation,
 		      u64 owner_objectid, u64 owner_offset, int pin);
 int btrfs_free_reserved_extent(struct btrfs_root *root, u64 start, u64 len);
@@ -1545,10 +1558,15 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *root,
 			       struct extent_io_tree *unpin);
 int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
-				struct btrfs_root *root,
-				u64 bytenr, u64 num_bytes,
-				u64 root_objectid, u64 ref_generation,
-				u64 owner, u64 owner_offset);
+			 struct btrfs_root *root,
+			 u64 bytenr, u64 num_bytes, u64 parent,
+			 u64 root_objectid, u64 ref_generation,
+			 u64 owner, u64 owner_offset);
+int btrfs_update_extent_ref(struct btrfs_trans_handle *trans,
+			    struct btrfs_root *root, u64 bytenr,
+			    u64 orig_parent, u64 parent,
+			    u64 root_objectid, u64 ref_generation,
+			    u64 owner, u64 owner_offset);
 int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
 				    struct btrfs_root *root);
 int btrfs_free_block_groups(struct btrfs_fs_info *info);
@@ -1561,7 +1579,9 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
 int btrfs_previous_item(struct btrfs_root *root,
 			struct btrfs_path *path, u64 min_objectid,
 			int type);
-
+int btrfs_set_item_key_safe(struct btrfs_trans_handle *trans,
+			    struct btrfs_root *root, struct btrfs_path *path,
+			    struct btrfs_key *new_key);
 struct extent_buffer *btrfs_root_node(struct btrfs_root *root);
 struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root);
 int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 25be96946a2f..d35ca6a3f513 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -882,8 +882,8 @@ int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
 	root->ref_cows = 0;
 
 	root->node = btrfs_alloc_free_block(trans, root, root->leafsize,
-					    BTRFS_TREE_LOG_OBJECTID,
-					    0, 0, 0, 0, 0);
+					    0, BTRFS_TREE_LOG_OBJECTID,
+					    trans->transid, 0, 0, 0);
 
 	btrfs_set_header_nritems(root->node, 0);
 	btrfs_set_header_level(root->node, 0);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 558fbe407368..5258923d621f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -29,6 +29,21 @@
 #include "locking.h"
 #include "ref-cache.h"
 
+#define PENDING_EXTENT_INSERT 0
+#define PENDING_EXTENT_DELETE 1
+#define PENDING_BACKREF_UPDATE 2
+
+struct pending_extent_op {
+	int type;
+	u64 bytenr;
+	u64 num_bytes;
+	u64 parent;
+	u64 orig_parent;
+	u64 generation;
+	u64 orig_generation;
+	int level;
+};
+
 static int finish_current_insert(struct btrfs_trans_handle *trans, struct
 				 btrfs_root *extent_root);
 static int del_pending_extents(struct btrfs_trans_handle *trans, struct
@@ -487,48 +502,15 @@ struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
 	return ret;
 }
 
-static u64 hash_extent_ref(u64 root_objectid, u64 ref_generation,
-			   u64 owner, u64 owner_offset)
-{
-	u32 high_crc = ~(u32)0;
-	u32 low_crc = ~(u32)0;
-	__le64 lenum;
-	lenum = cpu_to_le64(root_objectid);
-	high_crc = btrfs_crc32c(high_crc, &lenum, sizeof(lenum));
-	lenum = cpu_to_le64(ref_generation);
-	low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
-	if (owner >= BTRFS_FIRST_FREE_OBJECTID) {
-		lenum = cpu_to_le64(owner);
-		low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
-		lenum = cpu_to_le64(owner_offset);
-		low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
-	}
-	return ((u64)high_crc << 32) | (u64)low_crc;
-}
-
-static int match_extent_ref(struct extent_buffer *leaf,
-			    struct btrfs_extent_ref *disk_ref,
-			    struct btrfs_extent_ref *cpu_ref)
-{
-	int ret;
-	int len;
-
-	if (cpu_ref->objectid)
-		len = sizeof(*cpu_ref);
-	else
-		len = 2 * sizeof(u64);
-	ret = memcmp_extent_buffer(leaf, cpu_ref, (unsigned long)disk_ref,
-				   len);
-	return ret == 0;
-}
-
 /* simple helper to search for an existing extent at a given offset */
-int btrfs_lookup_extent(struct btrfs_root *root, struct btrfs_path *path,
-			u64 start, u64 len)
+int btrfs_lookup_extent(struct btrfs_root *root, u64 start, u64 len)
 {
 	int ret;
 	struct btrfs_key key;
+	struct btrfs_path *path;
 
+	path = btrfs_alloc_path();
+	BUG_ON(!path);
 	maybe_lock_mutex(root);
 	key.objectid = start;
 	key.offset = len;
@@ -536,72 +518,7 @@ int btrfs_lookup_extent(struct btrfs_root *root, struct btrfs_path *path,
 	ret = btrfs_search_slot(NULL, root->fs_info->extent_root, &key, path,
 				0, 0);
 	maybe_unlock_mutex(root);
-	return ret;
-}
-
-static int noinline lookup_extent_backref(struct btrfs_trans_handle *trans,
-					  struct btrfs_root *root,
-					  struct btrfs_path *path, u64 bytenr,
-					  u64 root_objectid,
-					  u64 ref_generation, u64 owner,
-					  u64 owner_offset, int del)
-{
-	u64 hash;
-	struct btrfs_key key;
-	struct btrfs_key found_key;
-	struct btrfs_extent_ref ref;
-	struct extent_buffer *leaf;
-	struct btrfs_extent_ref *disk_ref;
-	int ret;
-	int ret2;
-
-	btrfs_set_stack_ref_root(&ref, root_objectid);
-	btrfs_set_stack_ref_generation(&ref, ref_generation);
-	btrfs_set_stack_ref_objectid(&ref, owner);
-	btrfs_set_stack_ref_offset(&ref, owner_offset);
-
-	hash = hash_extent_ref(root_objectid, ref_generation, owner,
-			       owner_offset);
-	key.offset = hash;
-	key.objectid = bytenr;
-	key.type = BTRFS_EXTENT_REF_KEY;
-
-	while (1) {
-		ret = btrfs_search_slot(trans, root, &key, path,
-					del ? -1 : 0, del);
-		if (ret < 0)
-			goto out;
-		leaf = path->nodes[0];
-		if (ret != 0) {
-			u32 nritems = btrfs_header_nritems(leaf);
-			if (path->slots[0] >= nritems) {
-				ret2 = btrfs_next_leaf(root, path);
-				if (ret2)
-					goto out;
-				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)
-				goto out;
-			key.offset = found_key.offset;
-			if (del) {
-				btrfs_release_path(root, path);
-				continue;
-			}
-		}
-		disk_ref = btrfs_item_ptr(path->nodes[0],
-					  path->slots[0],
-					  struct btrfs_extent_ref);
-		if (match_extent_ref(path->nodes[0], disk_ref, &ref)) {
-			ret = 0;
-			goto out;
-		}
-		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-		key.offset = found_key.offset + 1;
-		btrfs_release_path(root, path);
-	}
-out:
+	btrfs_free_path(path);
 	return ret;
 }
 
@@ -622,7 +539,7 @@ out:
  * File extents can be referenced by:
  *
  * - multiple snapshots, subvolumes, or different generations in one subvol
- * - different files inside a single subvolume (in theory, not implemented yet)
+ * - different files inside a single subvolume
  * - different offsets inside a file (bookend extents in file.c)
  *
  * The extent ref structure has fields for:
@@ -631,119 +548,284 @@ out:
  * - Generation number of the tree holding the reference
  * - objectid of the file holding the reference
  * - offset in the file corresponding to the key holding the reference
+ * - number of references holding by parent node (alway 1 for tree blocks)
+ *
+ * Btree leaf may hold multiple references to a file extent. In most cases,
+ * these references are from same file and the corresponding offsets inside
+ * the file are close together. So inode objectid and offset in file are
+ * just hints, they provide hints about where in the btree the references
+ * can be found and when we can stop searching.
  *
  * When a file extent is allocated the fields are filled in:
- *     (root_key.objectid, trans->transid, inode objectid, offset in file)
+ *     (root_key.objectid, trans->transid, inode objectid, offset in file, 1)
  *
  * When a leaf is cow'd new references are added for every file extent found
- * in the leaf.  It looks the same as the create case, but trans->transid
- * will be different when the block is cow'd.
+ * in the leaf.  It looks similar to the create case, but trans->transid will
+ * be different when the block is cow'd.
  *
- *     (root_key.objectid, trans->transid, inode objectid, offset in file)
+ *     (root_key.objectid, trans->transid, inode objectid, offset in file,
+ *      number of references in the leaf)
  *
- * When a file extent is removed either during snapshot deletion or file
- * truncation, the corresponding back reference is found
- * by searching for:
+ * Because inode objectid and offset in file are just hints, they are not
+ * used when backrefs are deleted. When a file extent is removed either
+ * during snapshot deletion or file truncation, we find the corresponding
+ * back back reference and check the following fields.
  *
- *     (btrfs_header_owner(leaf), btrfs_header_generation(leaf),
- *      inode objectid, offset in file)
+ *     (btrfs_header_owner(leaf), btrfs_header_generation(leaf))
  *
  * Btree extents can be referenced by:
  *
  * - Different subvolumes
  * - Different generations of the same subvolume
  *
- * Storing sufficient information for a full reverse mapping of a btree
- * block would require storing the lowest key of the block in the backref,
- * and it would require updating that lowest key either before write out or
- * every time it changed.  Instead, the objectid of the lowest key is stored
- * along with the level of the tree block.  This provides a hint
- * about where in the btree the block can be found.  Searches through the
- * btree only need to look for a pointer to that block, so they stop one
- * level higher than the level recorded in the backref.
- *
- * Some btrees do not do reference counting on their extents.  These
- * include the extent tree and the tree of tree roots.  Backrefs for these
- * trees always have a generation of zero.
- *
  * When a tree block is created, back references are inserted:
  *
- * (root->root_key.objectid, trans->transid or zero, level, lowest_key_objectid)
+ * (root->root_key.objectid, trans->transid, level, 0, 1)
  *
- * When a tree block is cow'd in a reference counted root,
- * new back references are added for all the blocks it points to.
- * These are of the form (trans->transid will have increased since creation):
+ * When a tree block is cow'd, new back references are added for all the
+ * blocks it points to. If the tree block isn't in reference counted root,
+ * the old back references are removed. These new back references are of
+ * the form (trans->transid will have increased since creation):
  *
- * (root->root_key.objectid, trans->transid, level, lowest_key_objectid)
+ * (root->root_key.objectid, trans->transid, level, 0, 1)
  *
- * Because the lowest_key_objectid and the level are just hints
- * they are not used when backrefs are deleted.  When a backref is deleted:
+ * When a backref is in deleting, the following fields are checked:
  *
  * if backref was for a tree root:
- *     root_objectid = root->root_key.objectid
+ *     (btrfs_header_owner(itself), btrfs_header_generation(itself))
  * else
- *     root_objectid = btrfs_header_owner(parent)
+ *     (btrfs_header_owner(parent), btrfs_header_generation(parent))
  *
- * (root_objectid, btrfs_header_generation(parent) or zero, 0, 0)
+ * Back Reference Key composing:
  *
- * Back Reference Key hashing:
- *
- * Back references have four fields, each 64 bits long.  Unfortunately,
- * This is hashed into a single 64 bit number and placed into the key offset.
- * The key objectid corresponds to the first byte in the extent, and the
- * key type is set to BTRFS_EXTENT_REF_KEY
+ * The key objectid corresponds to the first byte in the extent, the key
+ * type is set to BTRFS_EXTENT_REF_KEY, and the key offset is the first
+ * byte of parent extent. If a extent is tree root, the key offset is set
+ * to the key objectid.
  */
-int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
-				 struct btrfs_root *root,
-				 struct btrfs_path *path, u64 bytenr,
-				 u64 root_objectid, u64 ref_generation,
-				 u64 owner, u64 owner_offset)
+
+static int noinline lookup_extent_backref(struct btrfs_trans_handle *trans,
+					  struct btrfs_root *root,
+					  struct btrfs_path *path, u64 bytenr,
+					  u64 parent, u64 ref_root,
+					  u64 ref_generation, int del)
 {
-	u64 hash;
 	struct btrfs_key key;
-	struct btrfs_extent_ref ref;
-	struct btrfs_extent_ref *disk_ref;
+	struct btrfs_extent_ref *ref;
+	struct extent_buffer *leaf;
 	int ret;
 
-	btrfs_set_stack_ref_root(&ref, root_objectid);
-	btrfs_set_stack_ref_generation(&ref, ref_generation);
-	btrfs_set_stack_ref_objectid(&ref, owner);
-	btrfs_set_stack_ref_offset(&ref, owner_offset);
+	key.objectid = bytenr;
+	key.type = BTRFS_EXTENT_REF_KEY;
+	key.offset = parent;
+
+	ret = btrfs_search_slot(trans, root, &key, path, del ? -1 : 0, 1);
+	if (ret < 0)
+		go