fs/btrfs/dir-item.c - linux/kernel/git/gregkh/char-misc - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2007 Oracle.  All rights reserved.
  */

 #include "messages.h"
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
 #include "accessors.h"
 #include "dir-item.h"

 /*
  * insert a name into a directory, doing overflow properly if there is a hash
  * collision.  data_size indicates how big the item inserted should be.  On
  * success a struct btrfs_dir_item pointer is returned, otherwise it is
  * an ERR_PTR.
  *
  * The name is not copied into the dir item, you have to do that yourself.
  */
 static struct btrfs_dir_item *insert_with_overflow(struct btrfs_trans_handle
 						   *trans,
 						   struct btrfs_root *root,
 						   struct btrfs_path *path,
 						   const struct btrfs_key *cpu_key,
 						   u32 data_size,
 						   const char *name,
 						   int name_len)
 {
 	int ret;
 	char *ptr;
 	struct extent_buffer *leaf;

 	ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
 	if (ret == -EEXIST) {
 		struct btrfs_dir_item *di;
 		di = btrfs_match_dir_item_name(path, name, name_len);
 		if (di)
 			return ERR_PTR(-EEXIST);
 		btrfs_extend_item(trans, path, data_size);
 	} else if (ret < 0)
 		return ERR_PTR(ret);
 	WARN_ON(ret > 0);
 	leaf = path->nodes[0];
 	ptr = btrfs_item_ptr(leaf, path->slots[0], char);
 	ASSERT(data_size <= btrfs_item_size(leaf, path->slots[0]));
 	ptr += btrfs_item_size(leaf, path->slots[0]) - data_size;
 	return (struct btrfs_dir_item *)ptr;
 }

 /*
  * xattrs work a lot like directories, this inserts an xattr item
  * into the tree
  */
 int btrfs_insert_xattr_item(struct btrfs_trans_handle *trans,
 			    struct btrfs_root *root,
 			    struct btrfs_path *path, u64 objectid,
 			    const char *name, u16 name_len,
 			    const void *data, u16 data_len)
 {
 	int ret = 0;
 	struct btrfs_dir_item *dir_item;
 	unsigned long name_ptr, data_ptr;
 	struct btrfs_key key, location;
 	struct btrfs_disk_key disk_key;
 	struct extent_buffer *leaf;
 	u32 data_size;

 	if (name_len + data_len > BTRFS_MAX_XATTR_SIZE(root->fs_info))
 		return -ENOSPC;

 	key.objectid = objectid;
 	key.type = BTRFS_XATTR_ITEM_KEY;
 	key.offset = btrfs_name_hash(name, name_len);

 	data_size = sizeof(*dir_item) + name_len + data_len;
 	dir_item = insert_with_overflow(trans, root, path, &key, data_size,
 					name, name_len);
 	if (IS_ERR(dir_item))
 		return PTR_ERR(dir_item);
 	memset(&location, 0, sizeof(location));

 	leaf = path->nodes[0];
 	btrfs_cpu_key_to_disk(&disk_key, &location);
 	btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
 	btrfs_set_dir_flags(leaf, dir_item, BTRFS_FT_XATTR);
 	btrfs_set_dir_name_len(leaf, dir_item, name_len);
 	btrfs_set_dir_transid(leaf, dir_item, trans->transid);
 	btrfs_set_dir_data_len(leaf, dir_item, data_len);
 	name_ptr = (unsigned long)(dir_item + 1);
 	data_ptr = (unsigned long)((char *)name_ptr + name_len);

 	write_extent_buffer(leaf, name, name_ptr, name_len);
 	write_extent_buffer(leaf, data, data_ptr, data_len);

 	return ret;
 }

 /*
  * insert a directory item in the tree, doing all the magic for
  * both indexes. 'dir' indicates which objectid to insert it into,
  * 'location' is the key to stuff into the directory item, 'type' is the
  * type of the inode we're pointing to, and 'index' is the sequence number
  * to use for the second index (if one is created).
  * Will return 0 or -ENOMEM
  */
 int btrfs_insert_dir_item(struct btrfs_trans_handle *trans,
 			  const struct fscrypt_str *name, struct btrfs_inode *dir,
 			  const struct btrfs_key *location, u8 type, u64 index)
 {
 	int ret = 0;
 	int ret2 = 0;
 	struct btrfs_root *root = dir->root;
 	struct btrfs_path *path;
 	struct btrfs_dir_item *dir_item;
 	struct extent_buffer *leaf;
 	unsigned long name_ptr;
 	struct btrfs_key key;
 	struct btrfs_disk_key disk_key;
 	u32 data_size;

 	key.objectid = btrfs_ino(dir);
 	key.type = BTRFS_DIR_ITEM_KEY;
 	key.offset = btrfs_name_hash(name->name, name->len);

 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;

 	btrfs_cpu_key_to_disk(&disk_key, location);

 	data_size = sizeof(*dir_item) + name->len;
 	dir_item = insert_with_overflow(trans, root, path, &key, data_size,
 					name->name, name->len);
 	if (IS_ERR(dir_item)) {
 		ret = PTR_ERR(dir_item);
 		if (ret == -EEXIST)
 			goto second_insert;
 		goto out_free;
 	}

 	if (IS_ENCRYPTED(&dir->vfs_inode))
 		type |= BTRFS_FT_ENCRYPTED;

 	leaf = path->nodes[0];
 	btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
 	btrfs_set_dir_flags(leaf, dir_item, type);
 	btrfs_set_dir_data_len(leaf, dir_item, 0);
 	btrfs_set_dir_name_len(leaf, dir_item, name->len);
 	btrfs_set_dir_transid(leaf, dir_item, trans->transid);
 	name_ptr = (unsigned long)(dir_item + 1);

 	write_extent_buffer(leaf, name->name, name_ptr, name->len);

 second_insert:
 	/* FIXME, use some real flag for selecting the extra index */
 	if (root == root->fs_info->tree_root) {
 		ret = 0;
 		goto out_free;
 	}
 	btrfs_release_path(path);

 	ret2 = btrfs_insert_delayed_dir_index(trans, name->name, name->len, dir,
 					      &disk_key, type, index);
 out_free:
 	btrfs_free_path(path);
 	if (ret)
 		return ret;
 	if (ret2)
 		return ret2;
 	return 0;
 }

 static struct btrfs_dir_item *btrfs_lookup_match_dir(
 			struct btrfs_trans_handle *trans,
 			struct btrfs_root *root, struct btrfs_path *path,
 			struct btrfs_key *key, const char *name,
 			int name_len, int mod)
 {
 	const int ins_len = (mod < 0 ? -1 : 0);
 	const int cow = (mod != 0);
 	int ret;

 	ret = btrfs_search_slot(trans, root, key, path, ins_len, cow);
 	if (ret < 0)
 		return ERR_PTR(ret);
 	if (ret > 0)
 		return ERR_PTR(-ENOENT);

 	return btrfs_match_dir_item_name(path, name, name_len);
 }

 /*
  * Lookup for a directory item by name.
  *
  * @trans:	The transaction handle to use. Can be NULL if @mod is 0.
  * @root:	The root of the target tree.
  * @path:	Path to use for the search.
  * @dir:	The inode number (objectid) of the directory.
  * @name:	The name associated to the directory entry we are looking for.
  * @name_len:	The length of the name.
  * @mod:	Used to indicate if the tree search is meant for a read only
  *		lookup, for a modification lookup or for a deletion lookup, so
  *		its value should be 0, 1 or -1, respectively.
  *
  * Returns: NULL if the dir item does not exists, an error pointer if an error
  * happened, or a pointer to a dir item if a dir item exists for the given name.
  */
 struct btrfs_dir_item *btrfs_lookup_dir_item(struct btrfs_trans_handle *trans,
 					     struct btrfs_root *root,
 					     struct btrfs_path *path, u64 dir,
 					     const struct fscrypt_str *name,
 					     int mod)
 {
 	struct btrfs_key key;
 	struct btrfs_dir_item *di;

 	key.objectid = dir;
 	key.type = BTRFS_DIR_ITEM_KEY;
 	key.offset = btrfs_name_hash(name->name, name->len);

 	di = btrfs_lookup_match_dir(trans, root, path, &key, name->name,
 				    name->len, mod);
 	if (IS_ERR(di) && PTR_ERR(di) == -ENOENT)
 		return NULL;

 	return di;
 }

 int btrfs_check_dir_item_collision(struct btrfs_root *root, u64 dir_ino,
 				   const struct fscrypt_str *name)
 {
 	int ret;
 	struct btrfs_key key;
 	struct btrfs_dir_item *di;
 	int data_size;
 	struct extent_buffer *leaf;
 	int slot;
 	BTRFS_PATH_AUTO_FREE(path);

 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;

 	key.objectid = dir_ino;
 	key.type = BTRFS_DIR_ITEM_KEY;
 	key.offset = btrfs_name_hash(name->name, name->len);

 	di = btrfs_lookup_match_dir(NULL, root, path, &key, name->name,
 				    name->len, 0);
 	if (IS_ERR(di)) {
 		ret = PTR_ERR(di);
 		/* Nothing found, we're safe */
 		if (ret == -ENOENT)
 			return 0;

 		if (ret < 0)
 			return ret;
 	}

 	/* we found an item, look for our name in the item */
 	if (di) {
 		/* our exact name was found */
 		return -EEXIST;
 	}

 	/* See if there is room in the item to insert this name. */
 	data_size = sizeof(*di) + name->len;
 	leaf = path->nodes[0];
 	slot = path->slots[0];
 	if (data_size + btrfs_item_size(leaf, slot) +
 	    sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root->fs_info)) {
 		return -EOVERFLOW;
 	}

 	/* Plenty of insertion room. */
 	return 0;
 }

 /*
  * Lookup for a directory index item by name and index number.
  *
  * @trans:	The transaction handle to use. Can be NULL if @mod is 0.
  * @root:	The root of the target tree.
  * @path:	Path to use for the search.
  * @dir:	The inode number (objectid) of the directory.
  * @index:	The index number.
  * @name:	The name associated to the directory entry we are looking for.
  * @name_len:	The length of the name.
  * @mod:	Used to indicate if the tree search is meant for a read only
  *		lookup, for a modification lookup or for a deletion lookup, so
  *		its value should be 0, 1 or -1, respectively.
  *
  * Returns: NULL if the dir index item does not exists, an error pointer if an
  * error happened, or a pointer to a dir item if the dir index item exists and
  * matches the criteria (name and index number).
  */
 struct btrfs_dir_item *
 btrfs_lookup_dir_index_item(struct btrfs_trans_handle *trans,
 			    struct btrfs_root *root,
 			    struct btrfs_path *path, u64 dir,
 			    u64 index, const struct fscrypt_str *name, int mod)
 {
 	struct btrfs_dir_item *di;
 	struct btrfs_key key;

 	key.objectid = dir;
 	key.type = BTRFS_DIR_INDEX_KEY;
 	key.offset = index;

 	di = btrfs_lookup_match_dir(trans, root, path, &key, name->name,
 				    name->len, mod);
 	if (di == ERR_PTR(-ENOENT))
 		return NULL;

 	return di;
 }

 struct btrfs_dir_item *
 btrfs_search_dir_index_item(struct btrfs_root *root, struct btrfs_path *path,
 			    u64 dirid, const struct fscrypt_str *name)
 {
 	struct btrfs_dir_item *di;
 	struct btrfs_key key;
 	int ret;

 	key.objectid = dirid;
 	key.type = BTRFS_DIR_INDEX_KEY;
 	key.offset = 0;

 	btrfs_for_each_slot(root, &key, &key, path, ret) {
 		if (key.objectid != dirid || key.type != BTRFS_DIR_INDEX_KEY)
 			break;

 		di = btrfs_match_dir_item_name(path, name->name, name->len);
 		if (di)
 			return di;
 	}
 	/* Adjust return code if the key was not found in the next leaf. */
 	if (ret >= 0)
 		ret = -ENOENT;

 	return ERR_PTR(ret);
 }

 struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle *trans,
 					  struct btrfs_root *root,
 					  struct btrfs_path *path, u64 dir,
 					  const char *name, u16 name_len,
 					  int mod)
 {
 	struct btrfs_key key;
 	struct btrfs_dir_item *di;

 	key.objectid = dir;
 	key.type = BTRFS_XATTR_ITEM_KEY;
 	key.offset = btrfs_name_hash(name, name_len);

 	di = btrfs_lookup_match_dir(trans, root, path, &key, name, name_len, mod);
 	if (IS_ERR(di) && PTR_ERR(di) == -ENOENT)
 		return NULL;

 	return di;
 }

 /*
  * helper function to look at the directory item pointed to by 'path'
  * this walks through all the entries in a dir item and finds one
  * for a specific name.
  */
 struct btrfs_dir_item *btrfs_match_dir_item_name(const struct btrfs_path *path,
 						 const char *name, int name_len)
 {
 	struct btrfs_dir_item *dir_item;
 	unsigned long name_ptr;
 	u32 total_len;
 	u32 cur = 0;
 	u32 this_len;
 	struct extent_buffer *leaf;

 	leaf = path->nodes[0];
 	dir_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dir_item);

 	total_len = btrfs_item_size(leaf, path->slots[0]);
 	while (cur < total_len) {
 		this_len = sizeof(*dir_item) +
 			btrfs_dir_name_len(leaf, dir_item) +
 			btrfs_dir_data_len(leaf, dir_item);
 		name_ptr = (unsigned long)(dir_item + 1);

 		if (btrfs_dir_name_len(leaf, dir_item) == name_len &&
 		    memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0)
 			return dir_item;

 		cur += this_len;
 		dir_item = (struct btrfs_dir_item *)((char *)dir_item +
 						     this_len);
 	}
 	return NULL;
 }

 /*
  * given a pointer into a directory item, delete it.  This
  * handles items that have more than one entry in them.
  */
 int btrfs_delete_one_dir_name(struct btrfs_trans_handle *trans,
 			      struct btrfs_root *root,
 			      struct btrfs_path *path,
 			      const struct btrfs_dir_item *di)
 {

 	struct extent_buffer *leaf;
 	u32 sub_item_len;
 	u32 item_len;
 	int ret = 0;

 	leaf = path->nodes[0];
 	sub_item_len = sizeof(*di) + btrfs_dir_name_len(leaf, di) +
 		btrfs_dir_data_len(leaf, di);
 	item_len = btrfs_item_size(leaf, path->slots[0]);
 	if (sub_item_len == item_len) {
 		ret = btrfs_del_item(trans, root, path);
 	} else {
 		/* MARKER */
 		unsigned long ptr = (unsigned long)di;
 		unsigned long start;

 		start = btrfs_item_ptr_offset(leaf, path->slots[0]);
 		memmove_extent_buffer(leaf, ptr, ptr + sub_item_len,
 			item_len - (ptr + sub_item_len - start));
 		btrfs_truncate_item(trans, path, item_len - sub_item_len, 1);
 	}
 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2007 Oracle. All rights reserved.
	*/

	#include "messages.h"
	#include "ctree.h"
	#include "disk-io.h"
	#include "transaction.h"
	#include "accessors.h"
	#include "dir-item.h"

	/*
	* insert a name into a directory, doing overflow properly if there is a hash
	* collision. data_size indicates how big the item inserted should be. On
	* success a struct btrfs_dir_item pointer is returned, otherwise it is
	* an ERR_PTR.
	*
	* The name is not copied into the dir item, you have to do that yourself.
	*/
	static struct btrfs_dir_item *insert_with_overflow(struct btrfs_trans_handle
	*trans,
	struct btrfs_root *root,
	struct btrfs_path *path,
	const struct btrfs_key *cpu_key,
	u32 data_size,
	const char *name,
	int name_len)
	{
	int ret;
	char *ptr;
	struct extent_buffer *leaf;

	ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
	if (ret == -EEXIST) {
	struct btrfs_dir_item *di;
	di = btrfs_match_dir_item_name(path, name, name_len);
	if (di)
	return ERR_PTR(-EEXIST);
	btrfs_extend_item(trans, path, data_size);
	} else if (ret < 0)
	return ERR_PTR(ret);
	WARN_ON(ret > 0);
	leaf = path->nodes[0];
	ptr = btrfs_item_ptr(leaf, path->slots[0], char);
	ASSERT(data_size <= btrfs_item_size(leaf, path->slots[0]));
	ptr += btrfs_item_size(leaf, path->slots[0]) - data_size;
	return (struct btrfs_dir_item *)ptr;
	}

	/*
	* xattrs work a lot like directories, this inserts an xattr item
	* into the tree
	*/
	int btrfs_insert_xattr_item(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_path *path, u64 objectid,
	const char *name, u16 name_len,
	const void *data, u16 data_len)
	{
	int ret = 0;
	struct btrfs_dir_item *dir_item;
	unsigned long name_ptr, data_ptr;
	struct btrfs_key key, location;
	struct btrfs_disk_key disk_key;
	struct extent_buffer *leaf;
	u32 data_size;

	if (name_len + data_len > BTRFS_MAX_XATTR_SIZE(root->fs_info))
	return -ENOSPC;

	key.objectid = objectid;
	key.type = BTRFS_XATTR_ITEM_KEY;
	key.offset = btrfs_name_hash(name, name_len);

	data_size = sizeof(*dir_item) + name_len + data_len;
	dir_item = insert_with_overflow(trans, root, path, &key, data_size,
	name, name_len);
	if (IS_ERR(dir_item))
	return PTR_ERR(dir_item);
	memset(&location, 0, sizeof(location));

	leaf = path->nodes[0];
	btrfs_cpu_key_to_disk(&disk_key, &location);
	btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
	btrfs_set_dir_flags(leaf, dir_item, BTRFS_FT_XATTR);
	btrfs_set_dir_name_len(leaf, dir_item, name_len);
	btrfs_set_dir_transid(leaf, dir_item, trans->transid);
	btrfs_set_dir_data_len(leaf, dir_item, data_len);
	name_ptr = (unsigned long)(dir_item + 1);
	data_ptr = (unsigned long)((char *)name_ptr + name_len);

	write_extent_buffer(leaf, name, name_ptr, name_len);
	write_extent_buffer(leaf, data, data_ptr, data_len);

	return ret;
	}

	/*
	* insert a directory item in the tree, doing all the magic for
	* both indexes. 'dir' indicates which objectid to insert it into,
	* 'location' is the key to stuff into the directory item, 'type' is the
	* type of the inode we're pointing to, and 'index' is the sequence number
	* to use for the second index (if one is created).
	* Will return 0 or -ENOMEM
	*/
	int btrfs_insert_dir_item(struct btrfs_trans_handle *trans,
	const struct fscrypt_str name, struct btrfs_inode dir,
	const struct btrfs_key *location, u8 type, u64 index)
	{
	int ret = 0;
	int ret2 = 0;
	struct btrfs_root *root = dir->root;
	struct btrfs_path *path;
	struct btrfs_dir_item *dir_item;
	struct extent_buffer *leaf;
	unsigned long name_ptr;
	struct btrfs_key key;
	struct btrfs_disk_key disk_key;
	u32 data_size;

	key.objectid = btrfs_ino(dir);
	key.type = BTRFS_DIR_ITEM_KEY;
	key.offset = btrfs_name_hash(name->name, name->len);

	path = btrfs_alloc_path();
	if (!path)
	return -ENOMEM;

	btrfs_cpu_key_to_disk(&disk_key, location);

	data_size = sizeof(*dir_item) + name->len;
	dir_item = insert_with_overflow(trans, root, path, &key, data_size,
	name->name, name->len);
	if (IS_ERR(dir_item)) {
	ret = PTR_ERR(dir_item);
	if (ret == -EEXIST)
	goto second_insert;
	goto out_free;
	}

	if (IS_ENCRYPTED(&dir->vfs_inode))
	type \|= BTRFS_FT_ENCRYPTED;

	leaf = path->nodes[0];
	btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
	btrfs_set_dir_flags(leaf, dir_item, type);
	btrfs_set_dir_data_len(leaf, dir_item, 0);
	btrfs_set_dir_name_len(leaf, dir_item, name->len);
	btrfs_set_dir_transid(leaf, dir_item, trans->transid);
	name_ptr = (unsigned long)(dir_item + 1);

	write_extent_buffer(leaf, name->name, name_ptr, name->len);

	second_insert:
	/* FIXME, use some real flag for selecting the extra index */
	if (root == root->fs_info->tree_root) {
	ret = 0;
	goto out_free;
	}
	btrfs_release_path(path);

	ret2 = btrfs_insert_delayed_dir_index(trans, name->name, name->len, dir,
	&disk_key, type, index);
	out_free:
	btrfs_free_path(path);
	if (ret)
	return ret;
	if (ret2)
	return ret2;
	return 0;
	}

	static struct btrfs_dir_item *btrfs_lookup_match_dir(
	struct btrfs_trans_handle *trans,
	struct btrfs_root root, struct btrfs_path path,
	struct btrfs_key key, const char name,
	int name_len, int mod)
	{
	const int ins_len = (mod < 0 ? -1 : 0);
	const int cow = (mod != 0);
	int ret;

	ret = btrfs_search_slot(trans, root, key, path, ins_len, cow);
	if (ret < 0)
	return ERR_PTR(ret);
	if (ret > 0)
	return ERR_PTR(-ENOENT);

	return btrfs_match_dir_item_name(path, name, name_len);
	}

	/*
	* Lookup for a directory item by name.
	*
	* @trans: The transaction handle to use. Can be NULL if @mod is 0.
	* @root: The root of the target tree.
	* @path: Path to use for the search.
	* @dir: The inode number (objectid) of the directory.
	* @name: The name associated to the directory entry we are looking for.
	* @name_len: The length of the name.
	* @mod: Used to indicate if the tree search is meant for a read only
	* lookup, for a modification lookup or for a deletion lookup, so
	* its value should be 0, 1 or -1, respectively.
	*
	* Returns: NULL if the dir item does not exists, an error pointer if an error
	* happened, or a pointer to a dir item if a dir item exists for the given name.
	*/
	struct btrfs_dir_item btrfs_lookup_dir_item(struct btrfs_trans_handle trans,
	struct btrfs_root *root,
	struct btrfs_path *path, u64 dir,
	const struct fscrypt_str *name,
	int mod)
	{
	struct btrfs_key key;
	struct btrfs_dir_item *di;

	key.objectid = dir;
	key.type = BTRFS_DIR_ITEM_KEY;
	key.offset = btrfs_name_hash(name->name, name->len);

	di = btrfs_lookup_match_dir(trans, root, path, &key, name->name,
	name->len, mod);
	if (IS_ERR(di) && PTR_ERR(di) == -ENOENT)
	return NULL;

	return di;
	}

	int btrfs_check_dir_item_collision(struct btrfs_root *root, u64 dir_ino,
	const struct fscrypt_str *name)
	{
	int ret;
	struct btrfs_key key;
	struct btrfs_dir_item *di;
	int data_size;
	struct extent_buffer *leaf;
	int slot;
	BTRFS_PATH_AUTO_FREE(path);

	path = btrfs_alloc_path();
	if (!path)
	return -ENOMEM;

	key.objectid = dir_ino;
	key.type = BTRFS_DIR_ITEM_KEY;
	key.offset = btrfs_name_hash(name->name, name->len);

	di = btrfs_lookup_match_dir(NULL, root, path, &key, name->name,
	name->len, 0);
	if (IS_ERR(di)) {
	ret = PTR_ERR(di);
	/* Nothing found, we're safe */
	if (ret == -ENOENT)
	return 0;

	if (ret < 0)
	return ret;
	}

	/* we found an item, look for our name in the item */
	if (di) {
	/* our exact name was found */
	return -EEXIST;
	}

	/* See if there is room in the item to insert this name. */
	data_size = sizeof(*di) + name->len;
	leaf = path->nodes[0];
	slot = path->slots[0];
	if (data_size + btrfs_item_size(leaf, slot) +
	sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root->fs_info)) {
	return -EOVERFLOW;
	}

	/* Plenty of insertion room. */
	return 0;
	}

	/*
	* Lookup for a directory index item by name and index number.
	*
	* @trans: The transaction handle to use. Can be NULL if @mod is 0.
	* @root: The root of the target tree.
	* @path: Path to use for the search.
	* @dir: The inode number (objectid) of the directory.
	* @index: The index number.
	* @name: The name associated to the directory entry we are looking for.
	* @name_len: The length of the name.
	* @mod: Used to indicate if the tree search is meant for a read only
	* lookup, for a modification lookup or for a deletion lookup, so
	* its value should be 0, 1 or -1, respectively.
	*
	* Returns: NULL if the dir index item does not exists, an error pointer if an
	* error happened, or a pointer to a dir item if the dir index item exists and
	* matches the criteria (name and index number).
	*/
	struct btrfs_dir_item *
	btrfs_lookup_dir_index_item(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_path *path, u64 dir,
	u64 index, const struct fscrypt_str *name, int mod)
	{
	struct btrfs_dir_item *di;
	struct btrfs_key key;

	key.objectid = dir;
	key.type = BTRFS_DIR_INDEX_KEY;
	key.offset = index;

	di = btrfs_lookup_match_dir(trans, root, path, &key, name->name,
	name->len, mod);
	if (di == ERR_PTR(-ENOENT))
	return NULL;

	return di;
	}

	struct btrfs_dir_item *
	btrfs_search_dir_index_item(struct btrfs_root root, struct btrfs_path path,
	u64 dirid, const struct fscrypt_str *name)
	{
	struct btrfs_dir_item *di;
	struct btrfs_key key;
	int ret;

	key.objectid = dirid;
	key.type = BTRFS_DIR_INDEX_KEY;
	key.offset = 0;

	btrfs_for_each_slot(root, &key, &key, path, ret) {
	if (key.objectid != dirid \|\| key.type != BTRFS_DIR_INDEX_KEY)
	break;

	di = btrfs_match_dir_item_name(path, name->name, name->len);
	if (di)
	return di;
	}
	/* Adjust return code if the key was not found in the next leaf. */
	if (ret >= 0)
	ret = -ENOENT;

	return ERR_PTR(ret);
	}

	struct btrfs_dir_item btrfs_lookup_xattr(struct btrfs_trans_handle trans,
	struct btrfs_root *root,
	struct btrfs_path *path, u64 dir,
	const char *name, u16 name_len,
	int mod)
	{
	struct btrfs_key key;
	struct btrfs_dir_item *di;

	key.objectid = dir;
	key.type = BTRFS_XATTR_ITEM_KEY;
	key.offset = btrfs_name_hash(name, name_len);

	di = btrfs_lookup_match_dir(trans, root, path, &key, name, name_len, mod);
	if (IS_ERR(di) && PTR_ERR(di) == -ENOENT)
	return NULL;

	return di;
	}

	/*
	* helper function to look at the directory item pointed to by 'path'
	* this walks through all the entries in a dir item and finds one
	* for a specific name.
	*/
	struct btrfs_dir_item btrfs_match_dir_item_name(const struct btrfs_path path,
	const char *name, int name_len)
	{
	struct btrfs_dir_item *dir_item;
	unsigned long name_ptr;
	u32 total_len;
	u32 cur = 0;
	u32 this_len;
	struct extent_buffer *leaf;

	leaf = path->nodes[0];
	dir_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dir_item);

	total_len = btrfs_item_size(leaf, path->slots[0]);
	while (cur < total_len) {
	this_len = sizeof(*dir_item) +
	btrfs_dir_name_len(leaf, dir_item) +
	btrfs_dir_data_len(leaf, dir_item);
	name_ptr = (unsigned long)(dir_item + 1);

	if (btrfs_dir_name_len(leaf, dir_item) == name_len &&
	memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0)
	return dir_item;

	cur += this_len;
	dir_item = (struct btrfs_dir_item )((char )dir_item +
	this_len);
	}
	return NULL;
	}

	/*
	* given a pointer into a directory item, delete it. This
	* handles items that have more than one entry in them.
	*/
	int btrfs_delete_one_dir_name(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_path *path,
	const struct btrfs_dir_item *di)
	{

	struct extent_buffer *leaf;
	u32 sub_item_len;
	u32 item_len;
	int ret = 0;

	leaf = path->nodes[0];
	sub_item_len = sizeof(*di) + btrfs_dir_name_len(leaf, di) +
	btrfs_dir_data_len(leaf, di);
	item_len = btrfs_item_size(leaf, path->slots[0]);
	if (sub_item_len == item_len) {
	ret = btrfs_del_item(trans, root, path);
	} else {
	/* MARKER */
	unsigned long ptr = (unsigned long)di;
	unsigned long start;

	start = btrfs_item_ptr_offset(leaf, path->slots[0]);
	memmove_extent_buffer(leaf, ptr, ptr + sub_item_len,
	item_len - (ptr + sub_item_len - start));
	btrfs_truncate_item(trans, path, item_len - sub_item_len, 1);
	}
	return ret;
	}