fs/btrfs/dir-item.c - linux - Git at Google

 /*
  * Copyright (C) 2007 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 "ctree.h"
 #include "disk-io.h"
 #include "hash.h"
 #include "transaction.h"

 static struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_root *root,
 			      struct btrfs_path *path,
 			      const char *name, int name_len);

 /*
  * 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,
 						   struct btrfs_key *cpu_key,
 						   u32 data_size,
 						   const char *name,
 						   int name_len)
 {
 	int ret;
 	char *ptr;
 	struct btrfs_item *item;
 	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(root, path, name, name_len);
 		if (di)
 			return ERR_PTR(-EEXIST);
 		btrfs_extend_item(root, path, data_size);
 	} else if (ret < 0)
 		return ERR_PTR(ret);
 	WARN_ON(ret > 0);
 	leaf = path->nodes[0];
 	item = btrfs_item_nr(path->slots[0]);
 	ptr = btrfs_item_ptr(leaf, path->slots[0], char);
 	BUG_ON(data_size > btrfs_item_size(leaf, item));
 	ptr += btrfs_item_size(leaf, item) - 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;

 	BUG_ON(name_len + data_len > BTRFS_MAX_XATTR_SIZE(root));

 	key.objectid = objectid;
 	btrfs_set_key_type(&key, 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_type(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);
 	btrfs_mark_buffer_dirty(path->nodes[0]);

 	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, struct btrfs_root
 			  *root, const char *name, int name_len,
 			  struct inode *dir, struct btrfs_key *location,
 			  u8 type, u64 index)
 {
 	int ret = 0;
 	int ret2 = 0;
 	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);
 	btrfs_set_key_type(&key, BTRFS_DIR_ITEM_KEY);
 	key.offset = btrfs_name_hash(name, name_len);

 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
 	path->leave_spinning = 1;

 	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_len);
 	if (IS_ERR(dir_item)) {
 		ret = PTR_ERR(dir_item);
 		if (ret == -EEXIST)
 			goto second_insert;
 		goto out_free;
 	}

 	leaf = path->nodes[0];
 	btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
 	btrfs_set_dir_type(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_ptr, name_len);
 	btrfs_mark_buffer_dirty(leaf);

 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, root, name, name_len, dir,
 					      &disk_key, type, index);
 out_free:
 	btrfs_free_path(path);
 	if (ret)
 		return ret;
 	if (ret2)
 		return ret2;
 	return 0;
 }

 /*
  * lookup a directory item based on name.  'dir' is the objectid
  * we're searching in, and 'mod' tells us if you plan on deleting the
  * item (use mod < 0) or changing the options (use mod > 0)
  */
 struct btrfs_dir_item *btrfs_lookup_dir_item(struct btrfs_trans_handle *trans,
 					     struct btrfs_root *root,
 					     struct btrfs_path *path, u64 dir,
 					     const char *name, int name_len,
 					     int mod)
 {
 	int ret;
 	struct btrfs_key key;
 	int ins_len = mod < 0 ? -1 : 0;
 	int cow = mod != 0;

 	key.objectid = dir;
 	btrfs_set_key_type(&key, BTRFS_DIR_ITEM_KEY);

 	key.offset = btrfs_name_hash(name, name_len);

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

 	return btrfs_match_dir_item_name(root, path, name, name_len);
 }

 int btrfs_check_dir_item_collision(struct btrfs_root *root, u64 dir,
 				   const char *name, int name_len)
 {
 	int ret;
 	struct btrfs_key key;
 	struct btrfs_dir_item *di;
 	int data_size;
 	struct extent_buffer *leaf;
 	int slot;
 	struct btrfs_path *path;


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

 	key.objectid = dir;
 	btrfs_set_key_type(&key, BTRFS_DIR_ITEM_KEY);
 	key.offset = btrfs_name_hash(name, name_len);

 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);

 	/* return back any errors */
 	if (ret < 0)
 		goto out;

 	/* nothing found, we're safe */
 	if (ret > 0) {
 		ret = 0;
 		goto out;
 	}

 	/* we found an item, look for our name in the item */
 	di = btrfs_match_dir_item_name(root, path, name, name_len);
 	if (di) {
 		/* our exact name was found */
 		ret = -EEXIST;
 		goto out;
 	}

 	/*
 	 * 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_nr(leaf, slot) +
 	    sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root)) {
 		ret = -EOVERFLOW;
 	} else {
 		/* plenty of insertion room */
 		ret = 0;
 	}
 out:
 	btrfs_free_path(path);
 	return ret;
 }

 /*
  * lookup a directory item based on index.  'dir' is the objectid
  * we're searching in, and 'mod' tells us if you plan on deleting the
  * item (use mod < 0) or changing the options (use mod > 0)
  *
  * The name is used to make sure the index really points to the name you were
  * looking for.
  */
 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 objectid, const char *name, int name_len,
 			    int mod)
 {
 	int ret;
 	struct btrfs_key key;
 	int ins_len = mod < 0 ? -1 : 0;
 	int cow = mod != 0;

 	key.objectid = dir;
 	btrfs_set_key_type(&key, BTRFS_DIR_INDEX_KEY);
 	key.offset = objectid;

 	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(root, path, name, name_len);
 }

 struct btrfs_dir_item *
 btrfs_search_dir_index_item(struct btrfs_root *root,
 			    struct btrfs_path *path, u64 dirid,
 			    const char *name, int name_len)
 {
 	struct extent_buffer *leaf;
 	struct btrfs_dir_item *di;
 	struct btrfs_key key;
 	u32 nritems;
 	int ret;

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

 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 	if (ret < 0)
 		return ERR_PTR(ret);

 	leaf = path->nodes[0];
 	nritems = btrfs_header_nritems(leaf);

 	while (1) {
 		if (path->slots[0] >= nritems) {
 			ret = btrfs_next_leaf(root, path);
 			if (ret < 0)
 				return ERR_PTR(ret);
 			if (ret > 0)
 				break;
 			leaf = path->nodes[0];
 			nritems = btrfs_header_nritems(leaf);
 			continue;
 		}

 		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 		if (key.objectid != dirid || key.type != BTRFS_DIR_INDEX_KEY)
 			break;

 		di = btrfs_match_dir_item_name(root, path, name, name_len);
 		if (di)
 			return di;

 		path->slots[0]++;
 	}
 	return NULL;
 }

 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)
 {
 	int ret;
 	struct btrfs_key key;
 	int ins_len = mod < 0 ? -1 : 0;
 	int cow = mod != 0;

 	key.objectid = dir;
 	btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
 	key.offset = btrfs_name_hash(name, name_len);
 	ret = btrfs_search_slot(trans, root, &key, path, ins_len, cow);
 	if (ret < 0)
 		return ERR_PTR(ret);
 	if (ret > 0)
 		return NULL;

 	return btrfs_match_dir_item_name(root, path, name, name_len);
 }

 /*
  * 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.
  */
 static struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_root *root,
 			      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);
 	if (verify_dir_item(root, leaf, dir_item))
 		return NULL;

 	total_len = btrfs_item_size_nr(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,
 			      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_nr(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(root, path, item_len - sub_item_len, 1);
 	}
 	return ret;
 }

 int verify_dir_item(struct btrfs_root *root,
 		    struct extent_buffer *leaf,
 		    struct btrfs_dir_item *dir_item)
 {
 	u16 namelen = BTRFS_NAME_LEN;
 	u8 type = btrfs_dir_type(leaf, dir_item);

 	if (type >= BTRFS_FT_MAX) {
 		btrfs_crit(root->fs_info, "invalid dir item type: %d",
 		       (int)type);
 		return 1;
 	}

 	if (type == BTRFS_FT_XATTR)
 		namelen = XATTR_NAME_MAX;

 	if (btrfs_dir_name_len(leaf, dir_item) > namelen) {
 		btrfs_crit(root->fs_info, "invalid dir item name len: %u",
 		       (unsigned)btrfs_dir_data_len(leaf, dir_item));
 		return 1;
 	}

 	/* BTRFS_MAX_XATTR_SIZE is the same for all dir items */
 	if ((btrfs_dir_data_len(leaf, dir_item) +
 	     btrfs_dir_name_len(leaf, dir_item)) > BTRFS_MAX_XATTR_SIZE(root)) {
 		btrfs_crit(root->fs_info, "invalid dir item name + data len: %u + %u",
 		       (unsigned)btrfs_dir_name_len(leaf, dir_item),
 		       (unsigned)btrfs_dir_data_len(leaf, dir_item));
 		return 1;
 	}

 	return 0;
 }
	/*
	* Copyright (C) 2007 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 "ctree.h"
	#include "disk-io.h"
	#include "hash.h"
	#include "transaction.h"

	static struct btrfs_dir_item btrfs_match_dir_item_name(struct btrfs_root root,
	struct btrfs_path *path,
	const char *name, int name_len);

	/*
	* 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,
	struct btrfs_key *cpu_key,
	u32 data_size,
	const char *name,
	int name_len)
	{
	int ret;
	char *ptr;
	struct btrfs_item *item;
	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(root, path, name, name_len);
	if (di)
	return ERR_PTR(-EEXIST);
	btrfs_extend_item(root, path, data_size);
	} else if (ret < 0)
	return ERR_PTR(ret);
	WARN_ON(ret > 0);
	leaf = path->nodes[0];
	item = btrfs_item_nr(path->slots[0]);
	ptr = btrfs_item_ptr(leaf, path->slots[0], char);
	BUG_ON(data_size > btrfs_item_size(leaf, item));
	ptr += btrfs_item_size(leaf, item) - 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;

	BUG_ON(name_len + data_len > BTRFS_MAX_XATTR_SIZE(root));

	key.objectid = objectid;
	btrfs_set_key_type(&key, 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_type(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);
	btrfs_mark_buffer_dirty(path->nodes[0]);

	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, struct btrfs_root
	root, const char name, int name_len,
	struct inode dir, struct btrfs_key location,
	u8 type, u64 index)
	{
	int ret = 0;
	int ret2 = 0;
	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);
	btrfs_set_key_type(&key, BTRFS_DIR_ITEM_KEY);
	key.offset = btrfs_name_hash(name, name_len);

	path = btrfs_alloc_path();
	if (!path)
	return -ENOMEM;
	path->leave_spinning = 1;

	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_len);
	if (IS_ERR(dir_item)) {
	ret = PTR_ERR(dir_item);
	if (ret == -EEXIST)
	goto second_insert;
	goto out_free;
	}

	leaf = path->nodes[0];
	btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
	btrfs_set_dir_type(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_ptr, name_len);
	btrfs_mark_buffer_dirty(leaf);

	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, root, name, name_len, dir,
	&disk_key, type, index);
	out_free:
	btrfs_free_path(path);
	if (ret)
	return ret;
	if (ret2)
	return ret2;
	return 0;
	}

	/*
	* lookup a directory item based on name. 'dir' is the objectid
	* we're searching in, and 'mod' tells us if you plan on deleting the
	* item (use mod < 0) or changing the options (use mod > 0)
	*/
	struct btrfs_dir_item btrfs_lookup_dir_item(struct btrfs_trans_handle trans,
	struct btrfs_root *root,
	struct btrfs_path *path, u64 dir,
	const char *name, int name_len,
	int mod)
	{
	int ret;
	struct btrfs_key key;
	int ins_len = mod < 0 ? -1 : 0;
	int cow = mod != 0;

	key.objectid = dir;
	btrfs_set_key_type(&key, BTRFS_DIR_ITEM_KEY);

	key.offset = btrfs_name_hash(name, name_len);

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

	return btrfs_match_dir_item_name(root, path, name, name_len);
	}

	int btrfs_check_dir_item_collision(struct btrfs_root *root, u64 dir,
	const char *name, int name_len)
	{
	int ret;
	struct btrfs_key key;
	struct btrfs_dir_item *di;
	int data_size;
	struct extent_buffer *leaf;
	int slot;
	struct btrfs_path *path;


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

	key.objectid = dir;
	btrfs_set_key_type(&key, BTRFS_DIR_ITEM_KEY);
	key.offset = btrfs_name_hash(name, name_len);

	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);

	/* return back any errors */
	if (ret < 0)
	goto out;

	/* nothing found, we're safe */
	if (ret > 0) {
	ret = 0;
	goto out;
	}

	/* we found an item, look for our name in the item */
	di = btrfs_match_dir_item_name(root, path, name, name_len);
	if (di) {
	/* our exact name was found */
	ret = -EEXIST;
	goto out;
	}

	/*
	* 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_nr(leaf, slot) +
	sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root)) {
	ret = -EOVERFLOW;
	} else {
	/* plenty of insertion room */
	ret = 0;
	}
	out:
	btrfs_free_path(path);
	return ret;
	}

	/*
	* lookup a directory item based on index. 'dir' is the objectid
	* we're searching in, and 'mod' tells us if you plan on deleting the
	* item (use mod < 0) or changing the options (use mod > 0)
	*
	* The name is used to make sure the index really points to the name you were
	* looking for.
	*/
	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 objectid, const char *name, int name_len,
	int mod)
	{
	int ret;
	struct btrfs_key key;
	int ins_len = mod < 0 ? -1 : 0;
	int cow = mod != 0;

	key.objectid = dir;
	btrfs_set_key_type(&key, BTRFS_DIR_INDEX_KEY);
	key.offset = objectid;

	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(root, path, name, name_len);
	}

	struct btrfs_dir_item *
	btrfs_search_dir_index_item(struct btrfs_root *root,
	struct btrfs_path *path, u64 dirid,
	const char *name, int name_len)
	{
	struct extent_buffer *leaf;
	struct btrfs_dir_item *di;
	struct btrfs_key key;
	u32 nritems;
	int ret;

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

	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
	if (ret < 0)
	return ERR_PTR(ret);

	leaf = path->nodes[0];
	nritems = btrfs_header_nritems(leaf);

	while (1) {
	if (path->slots[0] >= nritems) {
	ret = btrfs_next_leaf(root, path);
	if (ret < 0)
	return ERR_PTR(ret);
	if (ret > 0)
	break;
	leaf = path->nodes[0];
	nritems = btrfs_header_nritems(leaf);
	continue;
	}

	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
	if (key.objectid != dirid \|\| key.type != BTRFS_DIR_INDEX_KEY)
	break;

	di = btrfs_match_dir_item_name(root, path, name, name_len);
	if (di)
	return di;

	path->slots[0]++;
	}
	return NULL;
	}

	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)
	{
	int ret;
	struct btrfs_key key;
	int ins_len = mod < 0 ? -1 : 0;
	int cow = mod != 0;

	key.objectid = dir;
	btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
	key.offset = btrfs_name_hash(name, name_len);
	ret = btrfs_search_slot(trans, root, &key, path, ins_len, cow);
	if (ret < 0)
	return ERR_PTR(ret);
	if (ret > 0)
	return NULL;

	return btrfs_match_dir_item_name(root, path, name, name_len);
	}

	/*
	* 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.
	*/
	static struct btrfs_dir_item btrfs_match_dir_item_name(struct btrfs_root root,
	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);
	if (verify_dir_item(root, leaf, dir_item))
	return NULL;

	total_len = btrfs_item_size_nr(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,
	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_nr(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(root, path, item_len - sub_item_len, 1);
	}
	return ret;
	}

	int verify_dir_item(struct btrfs_root *root,
	struct extent_buffer *leaf,
	struct btrfs_dir_item *dir_item)
	{
	u16 namelen = BTRFS_NAME_LEN;
	u8 type = btrfs_dir_type(leaf, dir_item);

	if (type >= BTRFS_FT_MAX) {
	btrfs_crit(root->fs_info, "invalid dir item type: %d",
	(int)type);
	return 1;
	}

	if (type == BTRFS_FT_XATTR)
	namelen = XATTR_NAME_MAX;

	if (btrfs_dir_name_len(leaf, dir_item) > namelen) {
	btrfs_crit(root->fs_info, "invalid dir item name len: %u",
	(unsigned)btrfs_dir_data_len(leaf, dir_item));
	return 1;
	}

	/* BTRFS_MAX_XATTR_SIZE is the same for all dir items */
	if ((btrfs_dir_data_len(leaf, dir_item) +
	btrfs_dir_name_len(leaf, dir_item)) > BTRFS_MAX_XATTR_SIZE(root)) {
	btrfs_crit(root->fs_info, "invalid dir item name + data len: %u + %u",
	(unsigned)btrfs_dir_name_len(leaf, dir_item),
	(unsigned)btrfs_dir_data_len(leaf, dir_item));
	return 1;
	}

	return 0;
	}