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

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

 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
 #include "print-tree.h"

 struct btrfs_inode_ref *btrfs_find_name_in_backref(struct extent_buffer *leaf,
 						   int slot, const char *name,
 						   int name_len)
 {
 	struct btrfs_inode_ref *ref;
 	unsigned long ptr;
 	unsigned long name_ptr;
 	u32 item_size;
 	u32 cur_offset = 0;
 	int len;

 	item_size = btrfs_item_size_nr(leaf, slot);
 	ptr = btrfs_item_ptr_offset(leaf, slot);
 	while (cur_offset < item_size) {
 		ref = (struct btrfs_inode_ref *)(ptr + cur_offset);
 		len = btrfs_inode_ref_name_len(leaf, ref);
 		name_ptr = (unsigned long)(ref + 1);
 		cur_offset += len + sizeof(*ref);
 		if (len != name_len)
 			continue;
 		if (memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0)
 			return ref;
 	}
 	return NULL;
 }

 struct btrfs_inode_extref *btrfs_find_name_in_ext_backref(
 		struct extent_buffer *leaf, int slot, u64 ref_objectid,
 		const char *name, int name_len)
 {
 	struct btrfs_inode_extref *extref;
 	unsigned long ptr;
 	unsigned long name_ptr;
 	u32 item_size;
 	u32 cur_offset = 0;
 	int ref_name_len;

 	item_size = btrfs_item_size_nr(leaf, slot);
 	ptr = btrfs_item_ptr_offset(leaf, slot);

 	/*
 	 * Search all extended backrefs in this item. We're only
 	 * looking through any collisions so most of the time this is
 	 * just going to compare against one buffer. If all is well,
 	 * we'll return success and the inode ref object.
 	 */
 	while (cur_offset < item_size) {
 		extref = (struct btrfs_inode_extref *) (ptr + cur_offset);
 		name_ptr = (unsigned long)(&extref->name);
 		ref_name_len = btrfs_inode_extref_name_len(leaf, extref);

 		if (ref_name_len == name_len &&
 		    btrfs_inode_extref_parent(leaf, extref) == ref_objectid &&
 		    (memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0))
 			return extref;

 		cur_offset += ref_name_len + sizeof(*extref);
 	}
 	return NULL;
 }

 /* Returns NULL if no extref found */
 struct btrfs_inode_extref *
 btrfs_lookup_inode_extref(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root,
 			  struct btrfs_path *path,
 			  const char *name, int name_len,
 			  u64 inode_objectid, u64 ref_objectid, int ins_len,
 			  int cow)
 {
 	int ret;
 	struct btrfs_key key;

 	key.objectid = inode_objectid;
 	key.type = BTRFS_INODE_EXTREF_KEY;
 	key.offset = btrfs_extref_hash(ref_objectid, 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_find_name_in_ext_backref(path->nodes[0], path->slots[0],
 					      ref_objectid, name, name_len);

 }

 static int btrfs_del_inode_extref(struct btrfs_trans_handle *trans,
 				  struct btrfs_root *root,
 				  const char *name, int name_len,
 				  u64 inode_objectid, u64 ref_objectid,
 				  u64 *index)
 {
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct btrfs_inode_extref *extref;
 	struct extent_buffer *leaf;
 	int ret;
 	int del_len = name_len + sizeof(*extref);
 	unsigned long ptr;
 	unsigned long item_start;
 	u32 item_size;

 	key.objectid = inode_objectid;
 	key.type = BTRFS_INODE_EXTREF_KEY;
 	key.offset = btrfs_extref_hash(ref_objectid, name, name_len);

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

 	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 	if (ret > 0)
 		ret = -ENOENT;
 	if (ret < 0)
 		goto out;

 	/*
 	 * Sanity check - did we find the right item for this name?
 	 * This should always succeed so error here will make the FS
 	 * readonly.
 	 */
 	extref = btrfs_find_name_in_ext_backref(path->nodes[0], path->slots[0],
 						ref_objectid, name, name_len);
 	if (!extref) {
 		btrfs_handle_fs_error(root->fs_info, -ENOENT, NULL);
 		ret = -EROFS;
 		goto out;
 	}

 	leaf = path->nodes[0];
 	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 	if (index)
 		*index = btrfs_inode_extref_index(leaf, extref);

 	if (del_len == item_size) {
 		/*
 		 * Common case only one ref in the item, remove the
 		 * whole item.
 		 */
 		ret = btrfs_del_item(trans, root, path);
 		goto out;
 	}

 	ptr = (unsigned long)extref;
 	item_start = btrfs_item_ptr_offset(leaf, path->slots[0]);

 	memmove_extent_buffer(leaf, ptr, ptr + del_len,
 			      item_size - (ptr + del_len - item_start));

 	btrfs_truncate_item(path, item_size - del_len, 1);

 out:
 	btrfs_free_path(path);

 	return ret;
 }

 int btrfs_del_inode_ref(struct btrfs_trans_handle *trans,
 			struct btrfs_root *root,
 			const char *name, int name_len,
 			u64 inode_objectid, u64 ref_objectid, u64 *index)
 {
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct btrfs_inode_ref *ref;
 	struct extent_buffer *leaf;
 	unsigned long ptr;
 	unsigned long item_start;
 	u32 item_size;
 	u32 sub_item_len;
 	int ret;
 	int search_ext_refs = 0;
 	int del_len = name_len + sizeof(*ref);

 	key.objectid = inode_objectid;
 	key.offset = ref_objectid;
 	key.type = BTRFS_INODE_REF_KEY;

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

 	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 	if (ret > 0) {
 		ret = -ENOENT;
 		search_ext_refs = 1;
 		goto out;
 	} else if (ret < 0) {
 		goto out;
 	}

 	ref = btrfs_find_name_in_backref(path->nodes[0], path->slots[0], name,
 					 name_len);
 	if (!ref) {
 		ret = -ENOENT;
 		search_ext_refs = 1;
 		goto out;
 	}
 	leaf = path->nodes[0];
 	item_size = btrfs_item_size_nr(leaf, path->slots[0]);

 	if (index)
 		*index = btrfs_inode_ref_index(leaf, ref);

 	if (del_len == item_size) {
 		ret = btrfs_del_item(trans, root, path);
 		goto out;
 	}
 	ptr = (unsigned long)ref;
 	sub_item_len = name_len + sizeof(*ref);
 	item_start = btrfs_item_ptr_offset(leaf, path->slots[0]);
 	memmove_extent_buffer(leaf, ptr, ptr + sub_item_len,
 			      item_size - (ptr + sub_item_len - item_start));
 	btrfs_truncate_item(path, item_size - sub_item_len, 1);
 out:
 	btrfs_free_path(path);

 	if (search_ext_refs) {
 		/*
 		 * No refs were found, or we could not find the
 		 * name in our ref array. Find and remove the extended
 		 * inode ref then.
 		 */
 		return btrfs_del_inode_extref(trans, root, name, name_len,
 					      inode_objectid, ref_objectid, index);
 	}

 	return ret;
 }

 /*
  * btrfs_insert_inode_extref() - Inserts an extended inode ref into a tree.
  *
  * The caller must have checked against BTRFS_LINK_MAX already.
  */
 static int btrfs_insert_inode_extref(struct btrfs_trans_handle *trans,
 				     struct btrfs_root *root,
 				     const char *name, int name_len,
 				     u64 inode_objectid, u64 ref_objectid, u64 index)
 {
 	struct btrfs_inode_extref *extref;
 	int ret;
 	int ins_len = name_len + sizeof(*extref);
 	unsigned long ptr;
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct extent_buffer *leaf;
 	struct btrfs_item *item;

 	key.objectid = inode_objectid;
 	key.type = BTRFS_INODE_EXTREF_KEY;
 	key.offset = btrfs_extref_hash(ref_objectid, name, name_len);

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

 	ret = btrfs_insert_empty_item(trans, root, path, &key,
 				      ins_len);
 	if (ret == -EEXIST) {
 		if (btrfs_find_name_in_ext_backref(path->nodes[0],
 						   path->slots[0],
 						   ref_objectid,
 						   name, name_len))
 			goto out;

 		btrfs_extend_item(path, ins_len);
 		ret = 0;
 	}
 	if (ret < 0)
 		goto out;

 	leaf = path->nodes[0];
 	item = btrfs_item_nr(path->slots[0]);
 	ptr = (unsigned long)btrfs_item_ptr(leaf, path->slots[0], char);
 	ptr += btrfs_item_size(leaf, item) - ins_len;
 	extref = (struct btrfs_inode_extref *)ptr;

 	btrfs_set_inode_extref_name_len(path->nodes[0], extref, name_len);
 	btrfs_set_inode_extref_index(path->nodes[0], extref, index);
 	btrfs_set_inode_extref_parent(path->nodes[0], extref, ref_objectid);

 	ptr = (unsigned long)&extref->name;
 	write_extent_buffer(path->nodes[0], name, ptr, name_len);
 	btrfs_mark_buffer_dirty(path->nodes[0]);

 out:
 	btrfs_free_path(path);
 	return ret;
 }

 /* Will return 0, -ENOMEM, -EMLINK, or -EEXIST or anything from the CoW path */
 int btrfs_insert_inode_ref(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root,
 			   const char *name, int name_len,
 			   u64 inode_objectid, u64 ref_objectid, u64 index)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct btrfs_inode_ref *ref;
 	unsigned long ptr;
 	int ret;
 	int ins_len = name_len + sizeof(*ref);

 	key.objectid = inode_objectid;
 	key.offset = ref_objectid;
 	key.type = BTRFS_INODE_REF_KEY;

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

 	path->skip_release_on_error = 1;
 	ret = btrfs_insert_empty_item(trans, root, path, &key,
 				      ins_len);
 	if (ret == -EEXIST) {
 		u32 old_size;
 		ref = btrfs_find_name_in_backref(path->nodes[0], path->slots[0],
 						 name, name_len);
 		if (ref)
 			goto out;

 		old_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
 		btrfs_extend_item(path, ins_len);
 		ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
 				     struct btrfs_inode_ref);
 		ref = (struct btrfs_inode_ref *)((unsigned long)ref + old_size);
 		btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
 		btrfs_set_inode_ref_index(path->nodes[0], ref, index);
 		ptr = (unsigned long)(ref + 1);
 		ret = 0;
 	} else if (ret < 0) {
 		if (ret == -EOVERFLOW) {
 			if (btrfs_find_name_in_backref(path->nodes[0],
 						       path->slots[0],
 						       name, name_len))
 				ret = -EEXIST;
 			else
 				ret = -EMLINK;
 		}
 		goto out;
 	} else {
 		ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
 				     struct btrfs_inode_ref);
 		btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
 		btrfs_set_inode_ref_index(path->nodes[0], ref, index);
 		ptr = (unsigned long)(ref + 1);
 	}
 	write_extent_buffer(path->nodes[0], name, ptr, name_len);
 	btrfs_mark_buffer_dirty(path->nodes[0]);

 out:
 	btrfs_free_path(path);

 	if (ret == -EMLINK) {
 		struct btrfs_super_block *disk_super = fs_info->super_copy;
 		/* We ran out of space in the ref array. Need to
 		 * add an extended ref. */
 		if (btrfs_super_incompat_flags(disk_super)
 		    & BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF)
 			ret = btrfs_insert_inode_extref(trans, root, name,
 							name_len,
 							inode_objectid,
 							ref_objectid, index);
 	}

 	return ret;
 }

 int btrfs_insert_empty_inode(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     struct btrfs_path *path, u64 objectid)
 {
 	struct btrfs_key key;
 	int ret;
 	key.objectid = objectid;
 	key.type = BTRFS_INODE_ITEM_KEY;
 	key.offset = 0;

 	ret = btrfs_insert_empty_item(trans, root, path, &key,
 				      sizeof(struct btrfs_inode_item));
 	return ret;
 }

 int btrfs_lookup_inode(struct btrfs_trans_handle *trans, struct btrfs_root
 		       *root, struct btrfs_path *path,
 		       struct btrfs_key *location, int mod)
 {
 	int ins_len = mod < 0 ? -1 : 0;
 	int cow = mod != 0;
 	int ret;
 	int slot;
 	struct extent_buffer *leaf;
 	struct btrfs_key found_key;

 	ret = btrfs_search_slot(trans, root, location, path, ins_len, cow);
 	if (ret > 0 && location->type == BTRFS_ROOT_ITEM_KEY &&
 	    location->offset == (u64)-1 && path->slots[0] != 0) {
 		slot = path->slots[0] - 1;
 		leaf = path->nodes[0];
 		btrfs_item_key_to_cpu(leaf, &found_key, slot);
 		if (found_key.objectid == location->objectid &&
 		    found_key.type == location->type) {
 			path->slots[0]--;
 			return 0;
 		}
 	}
 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (C) 2007 Oracle. All rights reserved.
	*/

	#include "ctree.h"
	#include "disk-io.h"
	#include "transaction.h"
	#include "print-tree.h"

	struct btrfs_inode_ref btrfs_find_name_in_backref(struct extent_buffer leaf,
	int slot, const char *name,
	int name_len)
	{
	struct btrfs_inode_ref *ref;
	unsigned long ptr;
	unsigned long name_ptr;
	u32 item_size;
	u32 cur_offset = 0;
	int len;

	item_size = btrfs_item_size_nr(leaf, slot);
	ptr = btrfs_item_ptr_offset(leaf, slot);
	while (cur_offset < item_size) {
	ref = (struct btrfs_inode_ref *)(ptr + cur_offset);
	len = btrfs_inode_ref_name_len(leaf, ref);
	name_ptr = (unsigned long)(ref + 1);
	cur_offset += len + sizeof(*ref);
	if (len != name_len)
	continue;
	if (memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0)
	return ref;
	}
	return NULL;
	}

	struct btrfs_inode_extref *btrfs_find_name_in_ext_backref(
	struct extent_buffer *leaf, int slot, u64 ref_objectid,
	const char *name, int name_len)
	{
	struct btrfs_inode_extref *extref;
	unsigned long ptr;
	unsigned long name_ptr;
	u32 item_size;
	u32 cur_offset = 0;
	int ref_name_len;

	item_size = btrfs_item_size_nr(leaf, slot);
	ptr = btrfs_item_ptr_offset(leaf, slot);

	/*
	* Search all extended backrefs in this item. We're only
	* looking through any collisions so most of the time this is
	* just going to compare against one buffer. If all is well,
	* we'll return success and the inode ref object.
	*/
	while (cur_offset < item_size) {
	extref = (struct btrfs_inode_extref *) (ptr + cur_offset);
	name_ptr = (unsigned long)(&extref->name);
	ref_name_len = btrfs_inode_extref_name_len(leaf, extref);

	if (ref_name_len == name_len &&
	btrfs_inode_extref_parent(leaf, extref) == ref_objectid &&
	(memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0))
	return extref;

	cur_offset += ref_name_len + sizeof(*extref);
	}
	return NULL;
	}

	/* Returns NULL if no extref found */
	struct btrfs_inode_extref *
	btrfs_lookup_inode_extref(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_path *path,
	const char *name, int name_len,
	u64 inode_objectid, u64 ref_objectid, int ins_len,
	int cow)
	{
	int ret;
	struct btrfs_key key;

	key.objectid = inode_objectid;
	key.type = BTRFS_INODE_EXTREF_KEY;
	key.offset = btrfs_extref_hash(ref_objectid, 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_find_name_in_ext_backref(path->nodes[0], path->slots[0],
	ref_objectid, name, name_len);

	}

	static int btrfs_del_inode_extref(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	const char *name, int name_len,
	u64 inode_objectid, u64 ref_objectid,
	u64 *index)
	{
	struct btrfs_path *path;
	struct btrfs_key key;
	struct btrfs_inode_extref *extref;
	struct extent_buffer *leaf;
	int ret;
	int del_len = name_len + sizeof(*extref);
	unsigned long ptr;
	unsigned long item_start;
	u32 item_size;

	key.objectid = inode_objectid;
	key.type = BTRFS_INODE_EXTREF_KEY;
	key.offset = btrfs_extref_hash(ref_objectid, name, name_len);

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

	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret > 0)
	ret = -ENOENT;
	if (ret < 0)
	goto out;

	/*
	* Sanity check - did we find the right item for this name?
	* This should always succeed so error here will make the FS
	* readonly.
	*/
	extref = btrfs_find_name_in_ext_backref(path->nodes[0], path->slots[0],
	ref_objectid, name, name_len);
	if (!extref) {
	btrfs_handle_fs_error(root->fs_info, -ENOENT, NULL);
	ret = -EROFS;
	goto out;
	}

	leaf = path->nodes[0];
	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
	if (index)
	*index = btrfs_inode_extref_index(leaf, extref);

	if (del_len == item_size) {
	/*
	* Common case only one ref in the item, remove the
	* whole item.
	*/
	ret = btrfs_del_item(trans, root, path);
	goto out;
	}

	ptr = (unsigned long)extref;
	item_start = btrfs_item_ptr_offset(leaf, path->slots[0]);

	memmove_extent_buffer(leaf, ptr, ptr + del_len,
	item_size - (ptr + del_len - item_start));

	btrfs_truncate_item(path, item_size - del_len, 1);

	out:
	btrfs_free_path(path);

	return ret;
	}

	int btrfs_del_inode_ref(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	const char *name, int name_len,
	u64 inode_objectid, u64 ref_objectid, u64 *index)
	{
	struct btrfs_path *path;
	struct btrfs_key key;
	struct btrfs_inode_ref *ref;
	struct extent_buffer *leaf;
	unsigned long ptr;
	unsigned long item_start;
	u32 item_size;
	u32 sub_item_len;
	int ret;
	int search_ext_refs = 0;
	int del_len = name_len + sizeof(*ref);

	key.objectid = inode_objectid;
	key.offset = ref_objectid;
	key.type = BTRFS_INODE_REF_KEY;

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

	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret > 0) {
	ret = -ENOENT;
	search_ext_refs = 1;
	goto out;
	} else if (ret < 0) {
	goto out;
	}

	ref = btrfs_find_name_in_backref(path->nodes[0], path->slots[0], name,
	name_len);
	if (!ref) {
	ret = -ENOENT;
	search_ext_refs = 1;
	goto out;
	}
	leaf = path->nodes[0];
	item_size = btrfs_item_size_nr(leaf, path->slots[0]);

	if (index)
	*index = btrfs_inode_ref_index(leaf, ref);

	if (del_len == item_size) {
	ret = btrfs_del_item(trans, root, path);
	goto out;
	}
	ptr = (unsigned long)ref;
	sub_item_len = name_len + sizeof(*ref);
	item_start = btrfs_item_ptr_offset(leaf, path->slots[0]);
	memmove_extent_buffer(leaf, ptr, ptr + sub_item_len,
	item_size - (ptr + sub_item_len - item_start));
	btrfs_truncate_item(path, item_size - sub_item_len, 1);
	out:
	btrfs_free_path(path);

	if (search_ext_refs) {
	/*
	* No refs were found, or we could not find the
	* name in our ref array. Find and remove the extended
	* inode ref then.
	*/
	return btrfs_del_inode_extref(trans, root, name, name_len,
	inode_objectid, ref_objectid, index);
	}

	return ret;
	}

	/*
	* btrfs_insert_inode_extref() - Inserts an extended inode ref into a tree.
	*
	* The caller must have checked against BTRFS_LINK_MAX already.
	*/
	static int btrfs_insert_inode_extref(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	const char *name, int name_len,
	u64 inode_objectid, u64 ref_objectid, u64 index)
	{
	struct btrfs_inode_extref *extref;
	int ret;
	int ins_len = name_len + sizeof(*extref);
	unsigned long ptr;
	struct btrfs_path *path;
	struct btrfs_key key;
	struct extent_buffer *leaf;
	struct btrfs_item *item;

	key.objectid = inode_objectid;
	key.type = BTRFS_INODE_EXTREF_KEY;
	key.offset = btrfs_extref_hash(ref_objectid, name, name_len);

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

	ret = btrfs_insert_empty_item(trans, root, path, &key,
	ins_len);
	if (ret == -EEXIST) {
	if (btrfs_find_name_in_ext_backref(path->nodes[0],
	path->slots[0],
	ref_objectid,
	name, name_len))
	goto out;

	btrfs_extend_item(path, ins_len);
	ret = 0;
	}
	if (ret < 0)
	goto out;

	leaf = path->nodes[0];
	item = btrfs_item_nr(path->slots[0]);
	ptr = (unsigned long)btrfs_item_ptr(leaf, path->slots[0], char);
	ptr += btrfs_item_size(leaf, item) - ins_len;
	extref = (struct btrfs_inode_extref *)ptr;

	btrfs_set_inode_extref_name_len(path->nodes[0], extref, name_len);
	btrfs_set_inode_extref_index(path->nodes[0], extref, index);
	btrfs_set_inode_extref_parent(path->nodes[0], extref, ref_objectid);

	ptr = (unsigned long)&extref->name;
	write_extent_buffer(path->nodes[0], name, ptr, name_len);
	btrfs_mark_buffer_dirty(path->nodes[0]);

	out:
	btrfs_free_path(path);
	return ret;
	}

	/* Will return 0, -ENOMEM, -EMLINK, or -EEXIST or anything from the CoW path */
	int btrfs_insert_inode_ref(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	const char *name, int name_len,
	u64 inode_objectid, u64 ref_objectid, u64 index)
	{
	struct btrfs_fs_info *fs_info = root->fs_info;
	struct btrfs_path *path;
	struct btrfs_key key;
	struct btrfs_inode_ref *ref;
	unsigned long ptr;
	int ret;
	int ins_len = name_len + sizeof(*ref);

	key.objectid = inode_objectid;
	key.offset = ref_objectid;
	key.type = BTRFS_INODE_REF_KEY;

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

	path->skip_release_on_error = 1;
	ret = btrfs_insert_empty_item(trans, root, path, &key,
	ins_len);
	if (ret == -EEXIST) {
	u32 old_size;
	ref = btrfs_find_name_in_backref(path->nodes[0], path->slots[0],
	name, name_len);
	if (ref)
	goto out;

	old_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
	btrfs_extend_item(path, ins_len);
	ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
	struct btrfs_inode_ref);
	ref = (struct btrfs_inode_ref *)((unsigned long)ref + old_size);
	btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
	btrfs_set_inode_ref_index(path->nodes[0], ref, index);
	ptr = (unsigned long)(ref + 1);
	ret = 0;
	} else if (ret < 0) {
	if (ret == -EOVERFLOW) {
	if (btrfs_find_name_in_backref(path->nodes[0],
	path->slots[0],
	name, name_len))
	ret = -EEXIST;
	else
	ret = -EMLINK;
	}
	goto out;
	} else {
	ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
	struct btrfs_inode_ref);
	btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
	btrfs_set_inode_ref_index(path->nodes[0], ref, index);
	ptr = (unsigned long)(ref + 1);
	}
	write_extent_buffer(path->nodes[0], name, ptr, name_len);
	btrfs_mark_buffer_dirty(path->nodes[0]);

	out:
	btrfs_free_path(path);

	if (ret == -EMLINK) {
	struct btrfs_super_block *disk_super = fs_info->super_copy;
	/* We ran out of space in the ref array. Need to
	* add an extended ref. */
	if (btrfs_super_incompat_flags(disk_super)
	& BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF)
	ret = btrfs_insert_inode_extref(trans, root, name,
	name_len,
	inode_objectid,
	ref_objectid, index);
	}

	return ret;
	}

	int btrfs_insert_empty_inode(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_path *path, u64 objectid)
	{
	struct btrfs_key key;
	int ret;
	key.objectid = objectid;
	key.type = BTRFS_INODE_ITEM_KEY;
	key.offset = 0;

	ret = btrfs_insert_empty_item(trans, root, path, &key,
	sizeof(struct btrfs_inode_item));
	return ret;
	}

	int btrfs_lookup_inode(struct btrfs_trans_handle *trans, struct btrfs_root
	root, struct btrfs_path path,
	struct btrfs_key *location, int mod)
	{
	int ins_len = mod < 0 ? -1 : 0;
	int cow = mod != 0;
	int ret;
	int slot;
	struct extent_buffer *leaf;
	struct btrfs_key found_key;

	ret = btrfs_search_slot(trans, root, location, path, ins_len, cow);
	if (ret > 0 && location->type == BTRFS_ROOT_ITEM_KEY &&
	location->offset == (u64)-1 && path->slots[0] != 0) {
	slot = path->slots[0] - 1;
	leaf = path->nodes[0];
	btrfs_item_key_to_cpu(leaf, &found_key, slot);
	if (found_key.objectid == location->objectid &&
	found_key.type == location->type) {
	path->slots[0]--;
	return 0;
	}
	}
	return ret;
	}