btrfs: implement delayed inode items operation

Changelog V5 -> V6:
- Fix oom when the memory load is high, by storing the delayed nodes into the
  root's radix tree, and letting btrfs inodes go.

Changelog V4 -> V5:
- Fix the race on adding the delayed node to the inode, which is spotted by
  Chris Mason.
- Merge Chris Mason's incremental patch into this patch.
- Fix deadlock between readdir() and memory fault, which is reported by
  Itaru Kitayama.

Changelog V3 -> V4:
- Fix nested lock, which is reported by Itaru Kitayama, by updating space cache
  inode in time.

Changelog V2 -> V3:
- Fix the race between the delayed worker and the task which does delayed items
  balance, which is reported by Tsutomu Itoh.
- Modify the patch address David Sterba's comment.
- Fix the bug of the cpu recursion spinlock, reported by Chris Mason

Changelog V1 -> V2:
- break up the global rb-tree, use a list to manage the delayed nodes,
  which is created for every directory and file, and used to manage the
  delayed directory name index items and the delayed inode item.
- introduce a worker to deal with the delayed nodes.

Compare with Ext3/4, the performance of file creation and deletion on btrfs
is very poor. the reason is that btrfs must do a lot of b+ tree insertions,
such as inode item, directory name item, directory name index and so on.

If we can do some delayed b+ tree insertion or deletion, we can improve the
performance, so we made this patch which implemented delayed directory name
index insertion/deletion and delayed inode update.

Implementation:
- introduce a delayed root object into the filesystem, that use two lists to
  manage the delayed nodes which are created for every file/directory.
  One is used to manage all the delayed nodes that have delayed items. And the
  other is used to manage the delayed nodes which is waiting to be dealt with
  by the work thread.
- Every delayed node has two rb-tree, one is used to manage the directory name
  index which is going to be inserted into b+ tree, and the other is used to
  manage the directory name index which is going to be deleted from b+ tree.
- introduce a worker to deal with the delayed operation. This worker is used
  to deal with the works of the delayed directory name index items insertion
  and deletion and the delayed inode update.
  When the delayed items is beyond the lower limit, we create works for some
  delayed nodes and insert them into the work queue of the worker, and then
  go back.
  When the delayed items is beyond the upper bound, we create works for all
  the delayed nodes that haven't been dealt with, and insert them into the work
  queue of the worker, and then wait for that the untreated items is below some
  threshold value.
- When we want to insert a directory name index into b+ tree, we just add the
  information into the delayed inserting rb-tree.
  And then we check the number of the delayed items and do delayed items
  balance. (The balance policy is above.)
- When we want to delete a directory name index from the b+ tree, we search it
  in the inserting rb-tree at first. If we look it up, just drop it. If not,
  add the key of it into the delayed deleting rb-tree.
  Similar to the delayed inserting rb-tree, we also check the number of the
  delayed items and do delayed items balance.
  (The same to inserting manipulation)
- When we want to update the metadata of some inode, we cached the data of the
  inode into the delayed node. the worker will flush it into the b+ tree after
  dealing with the delayed insertion and deletion.
- We will move the delayed node to the tail of the list after we access the
  delayed node, By this way, we can cache more delayed items and merge more
  inode updates.
- If we want to commit transaction, we will deal with all the delayed node.
- the delayed node will be freed when we free the btrfs inode.
- Before we log the inode items, we commit all the directory name index items
  and the delayed inode update.

I did a quick test by the benchmark tool[1] and found we can improve the
performance of file creation by ~15%, and file deletion by ~20%.

Before applying this patch:
Create files:
        Total files: 50000
        Total time: 1.096108
        Average time: 0.000022
Delete files:
        Total files: 50000
        Total time: 1.510403
        Average time: 0.000030

After applying this patch:
Create files:
        Total files: 50000
        Total time: 0.932899
        Average time: 0.000019
Delete files:
        Total files: 50000
        Total time: 1.215732
        Average time: 0.000024

[1] http://marc.info/?l=linux-btrfs&m=128212635122920&q=p3

Many thanks for Kitayama-san's help!

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: David Sterba <dave@jikos.cz>
Tested-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Tested-by: Itaru Kitayama <kitayama@cl.bb4u.ne.jp>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

16 files changed, 2074 insertions, 91 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 31610ea73aec..a8411c22313d 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -7,4 +7,4 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.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 \
 	   export.o tree-log.o acl.o free-space-cache.o zlib.o lzo.o \
-	   compression.o delayed-ref.o relocation.o
+	   compression.o delayed-ref.o relocation.o delayed-inode.o
diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 57c3bb2884ce..beefafd91f22 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -22,6 +22,7 @@
 #include "extent_map.h"
 #include "extent_io.h"
 #include "ordered-data.h"
+#include "delayed-inode.h"
 
 /* in memory btrfs inode */
 struct btrfs_inode {
@@ -158,9 +159,13 @@ struct btrfs_inode {
 	 */
 	unsigned force_compress:4;
 
+	struct btrfs_delayed_node *delayed_node;
+
 	struct inode vfs_inode;
 };
 
+extern unsigned char btrfs_filetype_table[];
+
 static inline struct btrfs_inode *BTRFS_I(struct inode *inode)
 {
 	return container_of(inode, struct btrfs_inode, vfs_inode);
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 84d7ca1fe0ba..2736b6b2ff5f 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -38,11 +38,6 @@ static int balance_node_right(struct btrfs_trans_handle *trans,
 			      struct extent_buffer *src_buf);
 static int del_ptr(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 		   struct btrfs_path *path, int level, int slot);
-static int setup_items_for_insert(struct btrfs_trans_handle *trans,
-			struct btrfs_root *root, struct btrfs_path *path,
-			struct btrfs_key *cpu_key, u32 *data_size,
-			u32 total_data, u32 total_size, int nr);
-
 
 struct btrfs_path *btrfs_alloc_path(void)
 {
@@ -3559,11 +3554,10 @@ out:
  * to save stack depth by doing the bulk of the work in a function
  * that doesn't call btrfs_search_slot
  */
-static noinline_for_stack int
-setup_items_for_insert(struct btrfs_trans_handle *trans,
-		      struct btrfs_root *root, struct btrfs_path *path,
-		      struct btrfs_key *cpu_key, u32 *data_size,
-		      u32 total_data, u32 total_size, int nr)
+int setup_items_for_insert(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root, struct btrfs_path *path,
+			   struct btrfs_key *cpu_key, u32 *data_size,
+			   u32 total_data, u32 total_size, int nr)
 {
 	struct btrfs_item *item;
 	int i;
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8f4b81de3ae2..5d25129d0116 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -869,6 +869,7 @@ struct btrfs_block_group_cache {
 struct reloc_control;
 struct btrfs_device;
 struct btrfs_fs_devices;
+struct btrfs_delayed_root;
 struct btrfs_fs_info {
 	u8 fsid[BTRFS_FSID_SIZE];
 	u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
@@ -895,7 +896,10 @@ struct btrfs_fs_info {
 	/* logical->physical extent mapping */
 	struct btrfs_mapping_tree mapping_tree;
 
-	/* block reservation for extent, checksum and root tree */
+	/*
+	 * block reservation for extent, checksum, root tree and
+	 * delayed dir index item
+	 */
 	struct btrfs_block_rsv global_block_rsv;
 	/* block reservation for delay allocation */
 	struct btrfs_block_rsv delalloc_block_rsv;
@@ -1022,6 +1026,7 @@ struct btrfs_fs_info {
 	 * for the sys_munmap function call path
 	 */
 	struct btrfs_workers fixup_workers;
+	struct btrfs_workers delayed_workers;
 	struct task_struct *transaction_kthread;
 	struct task_struct *cleaner_kthread;
 	int thread_pool_size;
@@ -1079,6 +1084,8 @@ struct btrfs_fs_info {
 
 	/* filesystem state */
 	u64 fs_state;
+
+	struct btrfs_delayed_root *delayed_root;
 };
 
 /*
@@ -1162,6 +1169,11 @@ struct btrfs_root {
 	struct rb_root inode_tree;
 
 	/*
+	 * radix tree that keeps track of delayed nodes of every inode,
+	 * protected by inode_lock
+	 */
+	struct radix_tree_root delayed_nodes_tree;
+	/*
 	 * right now this just gets used so that a root has its own devid
 	 * for stat.  It may be used for more later
 	 */
@@ -2099,6 +2111,13 @@ static inline bool btrfs_mixed_space_info(struct btrfs_space_info *space_info)
 }
 
 /* extent-tree.c */
+static inline u64 btrfs_calc_trans_metadata_size(struct btrfs_root *root,
+						 int num_items)
+{
+	return (root->leafsize + root->nodesize * (BTRFS_MAX_LEVEL - 1)) *
+		3 * num_items;
+}
+
 void btrfs_put_block_group(struct btrfs_block_group_cache *cache);
 int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root, unsigned long count);
@@ -2294,6 +2313,8 @@ void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p);
 struct btrfs_path *btrfs_alloc_path(void);
 void btrfs_free_path(struct btrfs_path *p);
 void btrfs_set_path_blocking(struct btrfs_path *p);
+void btrfs_clear_path_blocking(struct btrfs_path *p,
+			       struct extent_buffer *held);
 void btrfs_unlock_up_safe(struct btrfs_path *p, int level);
 
 int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
@@ -2305,6 +2326,10 @@ static inline int btrfs_del_item(struct btrfs_trans_handle *trans,
 	return btrfs_del_items(trans, root, path, path->slots[0], 1);
 }
 
+int setup_items_for_insert(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root, struct btrfs_path *path,
+			   struct btrfs_key *cpu_key, u32 *data_size,
+			   u32 total_data, u32 total_size, int nr);
 int btrfs_insert_item(struct btrfs_trans_handle *trans, struct btrfs_root
 		      *root, struct btrfs_key *key, void *data, u32 data_size);
 int btrfs_insert_some_items(struct btrfs_trans_handle *trans,
@@ -2368,7 +2393,7 @@ void btrfs_check_and_init_root_item(struct btrfs_root_item *item);
 /* dir-item.c */
 int btrfs_insert_dir_item(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root, const char *name,
-			  int name_len, u64 dir,
+			  int name_len, struct inode *dir,
 			  struct btrfs_key *location, u8 type, u64 index);
 struct btrfs_dir_item *btrfs_lookup_dir_item(struct btrfs_trans_handle *trans,
 					     struct btrfs_root *root,
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
new file mode 100644
index 000000000000..95485318f001
--- /dev/null
+++ b/fs/btrfs/delayed-inode.c
@@ -0,0 +1,1694 @@
+/*
+ * Copyright (C) 2011 Fujitsu.  All rights reserved.
+ * Written by Miao Xie <miaox@cn.fujitsu.com>
+ *
+ * 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/slab.h>
+#include "delayed-inode.h"
+#include "disk-io.h"
+#include "transaction.h"
+
+#define BTRFS_DELAYED_WRITEBACK		400
+#define BTRFS_DELAYED_BACKGROUND	100
+
+static struct kmem_cache *delayed_node_cache;
+
+int __init btrfs_delayed_inode_init(void)
+{
+	delayed_node_cache = kmem_cache_create("delayed_node",
+					sizeof(struct btrfs_delayed_node),
+					0,
+					SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
+					NULL);
+	if (!delayed_node_cache)
+		return -ENOMEM;
+	return 0;
+}
+
+void btrfs_delayed_inode_exit(void)
+{
+	if (delayed_node_cache)
+		kmem_cache_destroy(delayed_node_cache);
+}
+
+static inline void btrfs_init_delayed_node(
+				struct btrfs_delayed_node *delayed_node,
+				struct btrfs_root *root, u64 inode_id)
+{
+	delayed_node->root = root;
+	delayed_node->inode_id = inode_id;
+	atomic_set(&delayed_node->refs, 0);
+	delayed_node->count = 0;
+	delayed_node->in_list = 0;
+	delayed_node->inode_dirty = 0;
+	delayed_node->ins_root = RB_ROOT;
+	delayed_node->del_root = RB_ROOT;
+	mutex_init(&delayed_node->mutex);
+	delayed_node->index_cnt = 0;
+	INIT_LIST_HEAD(&delayed_node->n_list);
+	INIT_LIST_HEAD(&delayed_node->p_list);
+	delayed_node->bytes_reserved = 0;
+}
+
+static inline int btrfs_is_continuous_delayed_item(
+					struct btrfs_delayed_item *item1,
+					struct btrfs_delayed_item *item2)
+{
+	if (item1->key.type == BTRFS_DIR_INDEX_KEY &&
+	    item1->key.objectid == item2->key.objectid &&
+	    item1->key.type == item2->key.type &&
+	    item1->key.offset + 1 == item2->key.offset)
+		return 1;
+	return 0;
+}
+
+static inline struct btrfs_delayed_root *btrfs_get_delayed_root(
+							struct btrfs_root *root)
+{
+	return root->fs_info->delayed_root;
+}
+
+static struct btrfs_delayed_node *btrfs_get_or_create_delayed_node(
+							struct inode *inode)
+{
+	struct btrfs_delayed_node *node;
+	struct btrfs_inode *btrfs_inode = BTRFS_I(inode);
+	struct btrfs_root *root = btrfs_inode->root;
+	int ret;
+
+again:
+	node = ACCESS_ONCE(btrfs_inode->delayed_node);
+	if (node) {
+		atomic_inc(&node->refs);	/* can be accessed */
+		return node;
+	}
+
+	spin_lock(&root->inode_lock);
+	node = radix_tree_lookup(&root->delayed_nodes_tree, inode->i_ino);
+	if (node) {
+		if (btrfs_inode->delayed_node) {
+			spin_unlock(&root->inode_lock);
+			goto again;
+		}
+		btrfs_inode->delayed_node = node;
+		atomic_inc(&node->refs);	/* can be accessed */
+		atomic_inc(&node->refs);	/* cached in the inode */
+		spin_unlock(&root->inode_lock);
+		return node;
+	}
+	spin_unlock(&root->inode_lock);
+
+	node = kmem_cache_alloc(delayed_node_cache, GFP_NOFS);
+	if (!node)
+		return ERR_PTR(-ENOMEM);
+	btrfs_init_delayed_node(node, root, inode->i_ino);
+
+	atomic_inc(&node->refs);	/* cached in the btrfs inode */
+	atomic_inc(&node->refs);	/* can be accessed */
+
+	ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
+	if (ret) {
+		kmem_cache_free(delayed_node_cache, node);
+		return ERR_PTR(ret);
+	}
+
+	spin_lock(&root->inode_lock);
+	ret = radix_tree_insert(&root->delayed_nodes_tree, inode->i_ino, node);
+	if (ret == -EEXIST) {
+		kmem_cache_free(delayed_node_cache, node);
+		spin_unlock(&root->inode_lock);
+		radix_tree_preload_end();
+		goto again;
+	}
+	btrfs_inode->delayed_node = node;
+	spin_unlock(&root->inode_lock);
+	radix_tree_preload_end();
+
+	return node;
+}
+
+/*
+ * Call it when holding delayed_node->mutex
+ *
+ * If mod = 1, add this node into the prepared list.
+ */
+static void btrfs_queue_delayed_node(struct btrfs_delayed_root *root,
+				     struct btrfs_delayed_node *node,
+				     int mod)
+{
+	spin_lock(&root->lock);
+	if (node->in_list) {
+		if (!list_empty(&node->p_list))
+			list_move_tail(&node->p_list, &root->prepare_list);
+		else if (mod)
+			list_add_tail(&node->p_list, &root->prepare_list);
+	} else {
+		list_add_tail(&node->n_list, &root->node_list);
+		list_add_tail(&node->p_list, &root->prepare_list);
+		atomic_inc(&node->refs);	/* inserted into list */
+		root->nodes++;
+		node->in_list = 1;
+	}
+	spin_unlock(&root->lock);
+}
+
+/* Call it when holding delayed_node->mutex */
+static void btrfs_dequeue_delayed_node(struct btrfs_delayed_root *root,
+				       struct btrfs_delayed_node *node)
+{
+	spin_lock(&root->lock);
+	if (node->in_list) {
+		root->nodes--;
+		atomic_dec(&node->refs);	/* not in the list */
+		list_del_init(&node->n_list);
+		if (!list_empty(&node->p_list))
+			list_del_init(&node->p_list);
+		node->in_list = 0;
+	}
+	spin_unlock(&root->lock);
+}
+
+struct btrfs_delayed_node *btrfs_first_delayed_node(
+			struct btrfs_delayed_root *delayed_root)
+{
+	struct list_head *p;
+	struct btrfs_delayed_node *node = NULL;
+
+	spin_lock(&delayed_root->lock);
+	if (list_empty(&delayed_root->node_list))
+		goto out;
+
+	p = delayed_root->node_list.next;
+	node = list_entry(p, struct btrfs_delayed_node, n_list);
+	atomic_inc(&node->refs);
+out:
+	spin_unlock(&delayed_root->lock);
+
+	return node;
+}
+
+struct btrfs_delayed_node *btrfs_next_delayed_node(
+						struct btrfs_delayed_node *node)
+{
+	struct btrfs_delayed_root *delayed_root;
+	struct list_head *p;
+	struct btrfs_delayed_node *next = NULL;
+
+	delayed_root = node->root->fs_info->delayed_root;
+	spin_lock(&delayed_root->lock);
+	if (!node->in_list) {	/* not in the list */
+		if (list_empty(&delayed_root->node_list))
+			goto out;
+		p = delayed_root->node_list.next;
+	} else if (list_is_last(&node->n_list, &delayed_root->node_list))
+		goto out;
+	else
+		p = node->n_list.next;
+
+	next = list_entry(p, struct btrfs_delayed_node, n_list);
+	atomic_inc(&next->refs);
+out:
+	spin_unlock(&delayed_root->lock);
+
+	return next;
+}
+
+static void __btrfs_release_delayed_node(
+				struct btrfs_delayed_node *delayed_node,
+				int mod)
+{
+	struct btrfs_delayed_root *delayed_root;
+
+	if (!delayed_node)
+		return;
+
+	delayed_root = delayed_node->root->fs_info->delayed_root;
+
+	mutex_lock(&delayed_node->mutex);
+	if (delayed_node->count)
+		btrfs_queue_delayed_node(delayed_root, delayed_node, mod);
+	else
+		btrfs_dequeue_delayed_node(delayed_root, delayed_node);
+	mutex_unlock(&delayed_node->mutex);
+
+	if (atomic_dec_and_test(&delayed_node->refs)) {
+		struct btrfs_root *root = delayed_node->root;
+		spin_lock(&root->inode_lock);
+		if (atomic_read(&delayed_node->refs) == 0) {
+			radix_tree_delete(&root->delayed_nodes_tree,
+					  delayed_node->inode_id);
+			kmem_cache_free(delayed_node_cache, delayed_node);
+		}
+		spin_unlock(&root->inode_lock);
+	}
+}
+
+static inline void btrfs_release_delayed_node(struct btrfs_delayed_node *node)
+{
+	__btrfs_release_delayed_node(node, 0);
+}
+
+struct btrfs_delayed_node *btrfs_first_prepared_delayed_node(
+					struct btrfs_delayed_root *delayed_root)
+{
+	struct list_head *p;
+	struct btrfs_delayed_node *node = NULL;
+
+	spin_lock(&delayed_root->lock);
+	if (list_empty(&delayed_root->prepare_list))
+		goto out;
+
+	p = delayed_root->prepare_list.next;
+	list_del_init(p);
+	node = list_entry(p, struct btrfs_delayed_node, p_list);
+	atomic_inc(&node->refs);
+out:
+	spin_unlock(&delayed_root->lock);
+
+	return node;
+}
+
+static inline void btrfs_release_prepared_delayed_node(
+					struct btrfs_delayed_node *node)
+{
+	__btrfs_release_delayed_node(node, 1);
+}
+
+struct btrfs_delayed_item *btrfs_alloc_delayed_item(u32 data_len)
+{
+	struct btrfs_delayed_item *item;
+	item = kmalloc(sizeof(*item) + data_len, GFP_NOFS);
+	if (item) {
+		item->data_len = data_len;
+		item->ins_or_del = 0;
+		item->bytes_reserved = 0;
+		item->block_rsv = NULL;
+		item->delayed_node = NULL;
+		atomic_set(&item->refs, 1);
+	}
+	return item;
+}
+
+/*
+ * __btrfs_lookup_delayed_item - look up the delayed item by key
+ * @delayed_node: pointer to the delayed node
+ * @key:	  the key to look up
+ * @prev:	  used to store the prev item if the right item isn't found
+ * @next:	  used to store the next item if the right item isn't found
+ *
+ * Note: if we don't find the right item, we will return the prev item and
+ * the next item.
+ */
+static struct btrfs_delayed_item *__btrfs_lookup_delayed_item(
+				struct rb_root *root,
+				struct btrfs_key *key,
+				struct btrfs_delayed_item **prev,
+				struct btrfs_delayed_item **next)
+{
+	struct rb_node *node, *prev_node = NULL;
+	struct btrfs_delayed_item *delayed_item = NULL;
+	int ret = 0;
+
+	node = root->rb_node;
+
+	while (node) {
+		delayed_item = rb_entry(node, struct btrfs_delayed_item,
+					rb_node);
+		prev_node = node;
+		ret = btrfs_comp_cpu_keys(&delayed_item->key, key);
+		if (ret < 0)
+			node = node->rb_right;
+		else if (ret > 0)
+			node = node->rb_left;
+		else
+			return delayed_item;
+	}
+
+	if (prev) {
+		if (!prev_node)
+			*prev = NULL;
+		else if (ret < 0)
+			*prev = delayed_item;
+		else if ((node = rb_prev(prev_node)) != NULL) {
+			*prev = rb_entry(node, struct btrfs_delayed_item,
+					 rb_node);
+		} else
+			*prev = NULL;
+	}
+
+	if (next) {
+		if (!prev_node)
+			*next = NULL;
+		else if (ret > 0)
+			*next = delayed_item;
+		else if ((node = rb_next(prev_node)) != NULL) {
+			*next = rb_entry(node, struct btrfs_delayed_item,
+					 rb_node);
+		} else
+			*next = NULL;
+	}
+	return NULL;
+}
+
+struct btrfs_delayed_item *__btrfs_lookup_delayed_insertion_item(
+					struct btrfs_delayed_node *delayed_node,
+					struct btrfs_key *key)
+{
+	struct btrfs_delayed_item *item;
+
+	item = __btrfs_lookup_delayed_item(&delayed_node->ins_root, key,
+					   NULL, NULL);
+	return item;
+}
+
+struct btrfs_delayed_item *__btrfs_lookup_delayed_deletion_item(
+					struct btrfs_delayed_node *delayed_node,
+					struct btrfs_key *key)
+{
+	struct btrfs_delayed_item *item;
+
+	item = __btrfs_lookup_delayed_item(&delayed_node->del_root, key,
+					   NULL, NULL);
+	return item;
+}
+
+struct btrfs_delayed_item *__btrfs_search_delayed_insertion_item(
+					struct btrfs_delayed_node *delayed_node,
+					struct btrfs_key *key)
+{
+	struct btrfs_delayed_item *item, *next;
+
+	item = __btrfs_lookup_delayed_item(&delayed_node->ins_root, key,
+					   NULL, &next);
+	if (!item)
+		item = next;
+
+	return item;
+}
+
+struct btrfs_delayed_item *__btrfs_search_delayed_deletion_item(
+					struct btrfs_delayed_node *delayed_node,
+					struct btrfs_key *key)
+{
+	struct btrfs_delayed_item *item, *next;
+
+	item = __btrfs_lookup_delayed_item(&delayed_node->del_root, key,
+					   NULL, &next);
+	if (!item)
+		item = next;
+
+	return item;
+}
+
+static int __btrfs_add_delayed_item(struct btrfs_delayed_node *delayed_node,
+				    struct btrfs_delayed_item *ins,
+				    int action)
+{
+	struct rb_node **p, *node;
+	struct rb_node *parent_node = NULL;
+	struct rb_root *root;
+	struct btrfs_delayed_item *item;
+	int cmp;
+
+	if (action == BTRFS_DELAYED_INSERTION_ITEM)
+		root = &delayed_node->ins_root;
+	else if (action == BTRFS_DELAYED_DELETION_ITEM)
+		root = &delayed_node->del_root;
+	else
+		BUG();
+	p = &root->rb_node;
+	node = &ins->rb_node;
+
+	while (*p) {
+		parent_node = *p;
+		item = rb_entry(parent_node, struct btrfs_delayed_item,
+				 rb_node);
+
+		cmp = btrfs_comp_cpu_keys(&item->key, &ins->key);
+		if (cmp < 0)
+			p = &(*p)->rb_right;
+		else if (cmp > 0)
+			p = &(*p)->rb_left;
+		else
+			return -EEXIST;
+	}
+
+	rb_link_node(node, parent_node, p);
+	rb_insert_color(node, root);
+	ins->delayed_node = delayed_node;
+	ins->ins_or_del = action;
+
+	if (ins->key.type == BTRFS_DIR_INDEX_KEY &&
+	    action == BTRFS_DELAYED_INSERTION_ITEM &&
+	    ins->key.offset >= delayed_node->index_cnt)
+			delayed_node->index_cnt = ins->key.offset + 1;
+
+	delayed_node->count++;
+	atomic_inc(&delayed_node->root->fs_info->delayed_root->items);
+	return 0;
+}
+
+static int __btrfs_add_delayed_insertion_item(struct btrfs_delayed_node *node,
+					      struct btrfs_delayed_item *item)
+{
+	return __btrfs_add_delayed_item(node, item,
+					BTRFS_DELAYED_INSERTION_ITEM);
+}
+
+static int __btrfs_add_delayed_deletion_item(struct btrfs_delayed_node *node,
+					     struct btrfs_delayed_item *item)
+{
+	return __btrfs_add_delayed_item(node, item,
+					BTRFS_DELAYED_DELETION_ITEM);
+}
+
+static void __btrfs_remove_delayed_item(struct btrfs_delayed_item *delayed_item)
+{
+	struct rb_root *root;
+	struct btrfs_delayed_root *delayed_root;
+
+	delayed_root = delayed_item->delayed_node->root->fs_info->delayed_root;
+
+	BUG_ON(!delayed_root);
+	BUG_ON(delayed_item->ins_or_del != BTRFS_DELAYED_DELETION_ITEM &&
+	       delayed_item->ins_or_del != BTRFS_DELAYED_INSERTION_ITEM);
+
+	if (delayed_item->ins_or_del == BTRFS_DELAYED_INSERTION_ITEM)
+		root = &delayed_item->delayed_node->ins_root;
+	else
+		root = &delayed_item->delayed_node->del_root;
+
+	rb_erase(&delayed_item->rb_node, root);
+	delayed_item->delayed_node->count--;
+	atomic_dec(&delayed_root->items);
+	if (atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND &&
+	    waitqueue_active(&delayed_root->wait))
+		wake_up(&delayed_root->wait);
+}
+
+static void btrfs_release_delayed_item(struct btrfs_delayed_item *item)
+{
+	if (item) {
+		__btrfs_remove_delayed_item(item);
+		if (atomic_dec_and_test(&item->refs))
+			kfree(item);
+	}
+}
+
+struct btrfs_delayed_item *__btrfs_first_delayed_insertion_item(
+					struct btrfs_delayed_node *delayed_node)
+{
+	struct rb_node *p;
+	struct btrfs_delayed_item *item = NULL;
+
+	p = rb_first(&delayed_node->ins_root);
+	if (p)
+		item = rb_entry(p, struct btrfs_delayed_item, rb_node);
+
+	return item;
+}
+
+struct btrfs_delayed_item *__btrfs_first_delayed_deletion_item(
+					struct btrfs_delayed_node *delayed_node)
+{
+	struct rb_node *p;
+	struct btrfs_delayed_item *item = NULL;
+
+	p = rb_first(&delayed_node->del_root);
+	if (p)
+		item = rb_entry(p, struct btrfs_delayed_item, rb_node);
+
+	return item;
+}
+
+struct btrfs_delayed_item *__btrfs_next_delayed_item(
+						struct btrfs_delayed_item *item)
+{
+	struct rb_node *p;
+	struct btrfs_delayed_item *next = NULL;
+
+	p = rb_next(&item->rb_node);
+	if (p)
+		next = rb_entry(p, struct btrfs_delayed_item, rb_node);
+
+	return next;
+}
+
+static inline struct btrfs_delayed_node *btrfs_get_delayed_node(
+							struct inode *inode)
+{
+	struct btrfs_inode *btrfs_inode = BTRFS_I(inode);
+	struct btrfs_delayed_node *delayed_node;
+
+	delayed_node = btrfs_inode->delayed_node;
+	if (delayed_node)
+		atomic_inc(&delayed_node->refs);
+
+	return delayed_node;
+}
+
+static inline struct btrfs_root *btrfs_get_fs_root(struct btrfs_root *root,
+						   u64 root_id)
+{
+	struct btrfs_key root_key;
+
+	if (root->objectid == root_id)
+		return root;
+
+	root_key.objectid = root_id;
+	root_key.type = BTRFS_ROOT_ITEM_KEY;
+	root_key.offset = (u64)-1;
+	return btrfs_read_fs_root_no_name(root->fs_info, &root_key);
+}
+
+static int btrfs_delayed_item_reserve_metadata(struct btrfs_trans_handle *trans,
+					       struct btrfs_root *root,
+					       struct btrfs_delayed_item *item)
+{
+	struct btrfs_block_rsv *src_rsv;
+	struct btrfs_block_rsv *dst_rsv;
+	u64 num_bytes;
+	int ret;
+
+	if (!trans->bytes_reserved)
+		return 0;
+
+	src_rsv = trans->block_rsv;
+	dst_rsv = &root->fs_info->global_block_rsv;
+
+	num_bytes = btrfs_calc_trans_metadata_size(root, 1);
+	ret = btrfs_block_rsv_migrate(src_rsv, dst_rsv, num_bytes);
+	if (!ret) {
+		item->bytes_reserved = num_bytes;
+		item->block_rsv = dst_rsv;
+	}
+
+	return ret;
+}
+
+static void btrfs_delayed_item_release_metadata(struct btrfs_root *root,
+						struct btrfs_delayed_item *item)
+{
+	if (!item->bytes_reserved)
+		return;
+
+	btrfs_block_rsv_release(root, item->block_rsv,
+				item->bytes_reserved);
+}
+
+static int btrfs_delayed_inode_reserve_metadata(
+					struct btrfs_trans_handle *trans,
+					struct btrfs_root *root,
+					struct btrfs_delayed_node *node)
+{
+	struct btrfs_block_rsv *src_rsv;
+	struct btrfs_block_rsv *dst_rsv;
+	u64 num_bytes;
+	int ret;
+
+	if (!trans->bytes_reserved)
+		return 0;
+
+	src_rsv = trans->block_rsv;
+	dst_rsv = &root->fs_info->global_block_rsv;
+
+	num_bytes = btrfs_calc_trans_metadata_size(root, 1);
+	ret = btrfs_block_rsv_migrate(src_rsv, dst_rsv, num_bytes);
+	if (!ret)
+		node->bytes_reserved = num_bytes;
+
+	return ret;
+}
+
+static void btrfs_delayed_inode_release_metadata(struct btrfs_root *root,
+						struct btrfs_delayed_node *node)
+{
+	struct btrfs_block_rsv *rsv;
+
+	if (!node->bytes_reserved)
+		return;
+
+	rsv = &root->fs_info->global_block_rsv;
+	btrfs_block_rsv_release(root, rsv,
+				node->bytes_reserved);
+	node->bytes_reserved = 0;
+}
+
+/*
+ * This helper will insert some continuous items into the same leaf according
+ * to the free space of the leaf.
+ */
+static int btrfs_batch_insert_items(struct btrfs_trans_handle *trans,
+				struct btrfs_root *root,
+				struct btrfs_path *path,
+				struct btrfs_delayed_item *item)
+{
+	struct btrfs_delayed_item *curr, *next;
+	int free_space;
+	int total_data_size = 0, total_size = 0;
+	struct extent_buffer *leaf;
+	char *data_ptr;
+	struct btrfs_key *keys;
+	u32 *data_size;
+	struct list_head head;
+	int slot;
+	int nitems;
+	int i;
+	int ret = 0;
+
+	BUG_ON(!path->nodes[0]);
+
+	leaf = path->nodes[0];
+	free_space = btrfs_leaf_free_space(root, leaf);
+	INIT_LIST_HEAD(&head);
+
+	next = item;
+
+	/*
+	 * count the number of the continuous items that we can insert in batch
+	 */
+	while (total_size + next->data_len + sizeof(struct btrfs_item) <=
+	       free_space) {
+		total_data_size += next->data_len;
+		total_size += next->data_len + sizeof(struct btrfs_item);
+		list_add_tail(&next->tree_list, &head);
+		nitems++;
+
+		curr = next;
+		next = __btrfs_next_delayed_item(curr);
+		if (!next)
+			break;
+
+		if (!btrfs_is_continuous_delayed_item(curr, next))
+			break;
+	}
+
+	if (!nitems) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * we need allocate some memory space, but it might cause the task
+	 * to sleep, so we set all locked nodes in the path to blocking locks
+	 * first.
+	 */
+	btrfs_set_path_blocking(path);
+
+	keys = kmalloc(sizeof(struct btrfs_key) * nitems, GFP_NOFS);
+	if (!keys) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	data_size = kmalloc(sizeof(u32) * nitems, GFP_NOFS);
+	if (!data_size) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	/* get keys of all the delayed items */
+	i = 0;
+	list_for_each_entry(next, &head, tree_list) {
+		keys[i] = next->key;
+		data_size[i] = next->data_len;
+		i++;
+	}
+
+	/* reset all the locked nodes in the patch to spinning locks. */
+	btrfs_clear_path_blocking(path, NULL);
+
+	/* insert the keys of the items */
+	ret = setup_items_for_insert(trans, root, path, keys, data_size,
+				     total_data_size, total_size, nitems);
+	if (ret)
+		goto error;
+
+	/* insert the dir index items */
+	slot = path->slots[0];
+	list_for_each_entry_safe(curr, next, &head, tree_list) {
+		data_ptr = btrfs_item_ptr(leaf, slot, char);
+		write_extent_buffer(leaf, &curr->data,
+				    (unsigned long)data_ptr,
+				    curr->data_len);
+		slot++;
+
+		btrfs_delayed_item_release_metadata(root, curr);
+
+		list_del(&curr->tree_list);
+		btrfs_release_delayed_item(curr);
+	}
+
+error:
+	kfree(data_size);
+	kfree(keys);
+out:
+	return ret;
+}
+
+/*
+ * This helper can just do simple insertion that needn't extend item for new
+ * data, such as directory name index insertion, inode insertion.
+ */
+static int btrfs_insert_delayed_item(struct btrfs_trans_handle *trans,
+				     struct btrfs_root *root,
+				     struct btrfs_path *path,
+				     struct btrfs_delayed_item *delayed_item)
+{
+	struct extent_buffer *leaf;
+	struct btrfs_item *item;
+	char *ptr;
+	int ret;
+
+	ret = btrfs_insert_empty_item(trans, root, path, &delayed_item->key,
+				      delayed_item->data_len);
+	if (ret < 0 && ret != -EEXIST)
+		return ret;