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![Filipe Manana](/assets/img/avatar_default.png)
Replacing a xattr consists of doing a lookup for its existing value, delete the current value from the respective leaf, release the search path and then finally insert the new value. This leaves a time window where readers (getxattr, listxattrs) won't see any value for the xattr. Xattrs are used to store ACLs, so this has security implications. This change also fixes 2 other existing issues which were: *) Deleting the old xattr value without verifying first if the new xattr will fit in the existing leaf item (in case multiple xattrs are packed in the same item due to name hash collision); *) Returning -EEXIST when the flag XATTR_CREATE is given and the xattr doesn't exist but we have have an existing item that packs muliple xattrs with the same name hash as the input xattr. In this case we should return ENOSPC. A test case for xfstests follows soon. Thanks to Alexandre Oliva for reporting the non-atomicity of the xattr replace implementation. Reported-by: Alexandre Oliva <oliva@gnu.org> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Chris Mason <clm@fb.com>
482 lines
13 KiB
C
482 lines
13 KiB
C
/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#include "ctree.h"
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#include "disk-io.h"
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#include "hash.h"
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#include "transaction.h"
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/*
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* insert a name into a directory, doing overflow properly if there is a hash
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* collision. data_size indicates how big the item inserted should be. On
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* success a struct btrfs_dir_item pointer is returned, otherwise it is
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* an ERR_PTR.
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*
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* The name is not copied into the dir item, you have to do that yourself.
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*/
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static struct btrfs_dir_item *insert_with_overflow(struct btrfs_trans_handle
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*trans,
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struct btrfs_root *root,
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struct btrfs_path *path,
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struct btrfs_key *cpu_key,
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u32 data_size,
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const char *name,
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int name_len)
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{
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int ret;
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char *ptr;
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struct btrfs_item *item;
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struct extent_buffer *leaf;
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ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
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if (ret == -EEXIST) {
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struct btrfs_dir_item *di;
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di = btrfs_match_dir_item_name(root, path, name, name_len);
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if (di)
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return ERR_PTR(-EEXIST);
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btrfs_extend_item(root, path, data_size);
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} else if (ret < 0)
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return ERR_PTR(ret);
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WARN_ON(ret > 0);
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leaf = path->nodes[0];
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item = btrfs_item_nr(path->slots[0]);
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ptr = btrfs_item_ptr(leaf, path->slots[0], char);
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BUG_ON(data_size > btrfs_item_size(leaf, item));
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ptr += btrfs_item_size(leaf, item) - data_size;
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return (struct btrfs_dir_item *)ptr;
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}
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/*
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* xattrs work a lot like directories, this inserts an xattr item
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* into the tree
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*/
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int btrfs_insert_xattr_item(struct btrfs_trans_handle *trans,
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struct btrfs_root *root,
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struct btrfs_path *path, u64 objectid,
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const char *name, u16 name_len,
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const void *data, u16 data_len)
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{
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int ret = 0;
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struct btrfs_dir_item *dir_item;
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unsigned long name_ptr, data_ptr;
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struct btrfs_key key, location;
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struct btrfs_disk_key disk_key;
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struct extent_buffer *leaf;
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u32 data_size;
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BUG_ON(name_len + data_len > BTRFS_MAX_XATTR_SIZE(root));
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key.objectid = objectid;
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key.type = BTRFS_XATTR_ITEM_KEY;
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key.offset = btrfs_name_hash(name, name_len);
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data_size = sizeof(*dir_item) + name_len + data_len;
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dir_item = insert_with_overflow(trans, root, path, &key, data_size,
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name, name_len);
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if (IS_ERR(dir_item))
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return PTR_ERR(dir_item);
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memset(&location, 0, sizeof(location));
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leaf = path->nodes[0];
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btrfs_cpu_key_to_disk(&disk_key, &location);
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btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
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btrfs_set_dir_type(leaf, dir_item, BTRFS_FT_XATTR);
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btrfs_set_dir_name_len(leaf, dir_item, name_len);
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btrfs_set_dir_transid(leaf, dir_item, trans->transid);
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btrfs_set_dir_data_len(leaf, dir_item, data_len);
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name_ptr = (unsigned long)(dir_item + 1);
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data_ptr = (unsigned long)((char *)name_ptr + name_len);
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write_extent_buffer(leaf, name, name_ptr, name_len);
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write_extent_buffer(leaf, data, data_ptr, data_len);
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btrfs_mark_buffer_dirty(path->nodes[0]);
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return ret;
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}
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/*
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* insert a directory item in the tree, doing all the magic for
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* both indexes. 'dir' indicates which objectid to insert it into,
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* 'location' is the key to stuff into the directory item, 'type' is the
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* type of the inode we're pointing to, and 'index' is the sequence number
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* to use for the second index (if one is created).
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* Will return 0 or -ENOMEM
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*/
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int btrfs_insert_dir_item(struct btrfs_trans_handle *trans, struct btrfs_root
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*root, const char *name, int name_len,
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struct inode *dir, struct btrfs_key *location,
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u8 type, u64 index)
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{
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int ret = 0;
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int ret2 = 0;
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struct btrfs_path *path;
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struct btrfs_dir_item *dir_item;
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struct extent_buffer *leaf;
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unsigned long name_ptr;
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struct btrfs_key key;
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struct btrfs_disk_key disk_key;
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u32 data_size;
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key.objectid = btrfs_ino(dir);
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key.type = BTRFS_DIR_ITEM_KEY;
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key.offset = btrfs_name_hash(name, name_len);
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path = btrfs_alloc_path();
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if (!path)
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return -ENOMEM;
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path->leave_spinning = 1;
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btrfs_cpu_key_to_disk(&disk_key, location);
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data_size = sizeof(*dir_item) + name_len;
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dir_item = insert_with_overflow(trans, root, path, &key, data_size,
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name, name_len);
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if (IS_ERR(dir_item)) {
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ret = PTR_ERR(dir_item);
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if (ret == -EEXIST)
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goto second_insert;
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goto out_free;
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}
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leaf = path->nodes[0];
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btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
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btrfs_set_dir_type(leaf, dir_item, type);
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btrfs_set_dir_data_len(leaf, dir_item, 0);
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btrfs_set_dir_name_len(leaf, dir_item, name_len);
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btrfs_set_dir_transid(leaf, dir_item, trans->transid);
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name_ptr = (unsigned long)(dir_item + 1);
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write_extent_buffer(leaf, name, name_ptr, name_len);
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btrfs_mark_buffer_dirty(leaf);
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second_insert:
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/* FIXME, use some real flag for selecting the extra index */
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if (root == root->fs_info->tree_root) {
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ret = 0;
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goto out_free;
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}
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btrfs_release_path(path);
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ret2 = btrfs_insert_delayed_dir_index(trans, root, name, name_len, dir,
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&disk_key, type, index);
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out_free:
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btrfs_free_path(path);
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if (ret)
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return ret;
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if (ret2)
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return ret2;
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return 0;
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}
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/*
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* lookup a directory item based on name. 'dir' is the objectid
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* we're searching in, and 'mod' tells us if you plan on deleting the
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* item (use mod < 0) or changing the options (use mod > 0)
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*/
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struct btrfs_dir_item *btrfs_lookup_dir_item(struct btrfs_trans_handle *trans,
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struct btrfs_root *root,
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struct btrfs_path *path, u64 dir,
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const char *name, int name_len,
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int mod)
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{
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int ret;
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struct btrfs_key key;
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int ins_len = mod < 0 ? -1 : 0;
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int cow = mod != 0;
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key.objectid = dir;
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key.type = BTRFS_DIR_ITEM_KEY;
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key.offset = btrfs_name_hash(name, name_len);
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ret = btrfs_search_slot(trans, root, &key, path, ins_len, cow);
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if (ret < 0)
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return ERR_PTR(ret);
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if (ret > 0)
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return NULL;
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return btrfs_match_dir_item_name(root, path, name, name_len);
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}
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int btrfs_check_dir_item_collision(struct btrfs_root *root, u64 dir,
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const char *name, int name_len)
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{
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int ret;
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struct btrfs_key key;
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struct btrfs_dir_item *di;
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int data_size;
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struct extent_buffer *leaf;
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int slot;
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struct btrfs_path *path;
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path = btrfs_alloc_path();
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if (!path)
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return -ENOMEM;
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key.objectid = dir;
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key.type = BTRFS_DIR_ITEM_KEY;
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key.offset = btrfs_name_hash(name, name_len);
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ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
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/* return back any errors */
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if (ret < 0)
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goto out;
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/* nothing found, we're safe */
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if (ret > 0) {
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ret = 0;
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goto out;
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}
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/* we found an item, look for our name in the item */
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di = btrfs_match_dir_item_name(root, path, name, name_len);
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if (di) {
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/* our exact name was found */
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ret = -EEXIST;
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goto out;
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}
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/*
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* see if there is room in the item to insert this
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* name
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*/
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data_size = sizeof(*di) + name_len;
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leaf = path->nodes[0];
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slot = path->slots[0];
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if (data_size + btrfs_item_size_nr(leaf, slot) +
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sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root)) {
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ret = -EOVERFLOW;
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} else {
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/* plenty of insertion room */
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ret = 0;
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}
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out:
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btrfs_free_path(path);
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return ret;
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}
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/*
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* lookup a directory item based on index. 'dir' is the objectid
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* we're searching in, and 'mod' tells us if you plan on deleting the
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* item (use mod < 0) or changing the options (use mod > 0)
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*
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* The name is used to make sure the index really points to the name you were
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* looking for.
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*/
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struct btrfs_dir_item *
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btrfs_lookup_dir_index_item(struct btrfs_trans_handle *trans,
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struct btrfs_root *root,
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struct btrfs_path *path, u64 dir,
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u64 objectid, const char *name, int name_len,
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int mod)
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{
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int ret;
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struct btrfs_key key;
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int ins_len = mod < 0 ? -1 : 0;
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int cow = mod != 0;
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key.objectid = dir;
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key.type = BTRFS_DIR_INDEX_KEY;
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key.offset = objectid;
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ret = btrfs_search_slot(trans, root, &key, path, ins_len, cow);
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if (ret < 0)
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return ERR_PTR(ret);
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if (ret > 0)
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return ERR_PTR(-ENOENT);
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return btrfs_match_dir_item_name(root, path, name, name_len);
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}
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struct btrfs_dir_item *
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btrfs_search_dir_index_item(struct btrfs_root *root,
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struct btrfs_path *path, u64 dirid,
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const char *name, int name_len)
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{
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struct extent_buffer *leaf;
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struct btrfs_dir_item *di;
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struct btrfs_key key;
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u32 nritems;
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int ret;
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key.objectid = dirid;
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key.type = BTRFS_DIR_INDEX_KEY;
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key.offset = 0;
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ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
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if (ret < 0)
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return ERR_PTR(ret);
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leaf = path->nodes[0];
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nritems = btrfs_header_nritems(leaf);
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while (1) {
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if (path->slots[0] >= nritems) {
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ret = btrfs_next_leaf(root, path);
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if (ret < 0)
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return ERR_PTR(ret);
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if (ret > 0)
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break;
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leaf = path->nodes[0];
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nritems = btrfs_header_nritems(leaf);
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continue;
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}
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btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
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if (key.objectid != dirid || key.type != BTRFS_DIR_INDEX_KEY)
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break;
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di = btrfs_match_dir_item_name(root, path, name, name_len);
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if (di)
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return di;
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path->slots[0]++;
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}
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return NULL;
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}
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struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle *trans,
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struct btrfs_root *root,
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struct btrfs_path *path, u64 dir,
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const char *name, u16 name_len,
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int mod)
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{
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int ret;
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struct btrfs_key key;
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int ins_len = mod < 0 ? -1 : 0;
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int cow = mod != 0;
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key.objectid = dir;
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key.type = BTRFS_XATTR_ITEM_KEY;
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key.offset = btrfs_name_hash(name, name_len);
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ret = btrfs_search_slot(trans, root, &key, path, ins_len, cow);
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if (ret < 0)
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return ERR_PTR(ret);
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if (ret > 0)
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return NULL;
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return btrfs_match_dir_item_name(root, path, name, name_len);
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}
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/*
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* helper function to look at the directory item pointed to by 'path'
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* this walks through all the entries in a dir item and finds one
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* for a specific name.
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*/
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struct btrfs_dir_item *btrfs_match_dir_item_name(struct btrfs_root *root,
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struct btrfs_path *path,
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const char *name, int name_len)
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{
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struct btrfs_dir_item *dir_item;
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unsigned long name_ptr;
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u32 total_len;
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u32 cur = 0;
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u32 this_len;
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struct extent_buffer *leaf;
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leaf = path->nodes[0];
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dir_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dir_item);
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if (verify_dir_item(root, leaf, dir_item))
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return NULL;
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total_len = btrfs_item_size_nr(leaf, path->slots[0]);
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while (cur < total_len) {
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this_len = sizeof(*dir_item) +
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btrfs_dir_name_len(leaf, dir_item) +
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btrfs_dir_data_len(leaf, dir_item);
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name_ptr = (unsigned long)(dir_item + 1);
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if (btrfs_dir_name_len(leaf, dir_item) == name_len &&
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memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0)
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return dir_item;
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cur += this_len;
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dir_item = (struct btrfs_dir_item *)((char *)dir_item +
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this_len);
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}
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return NULL;
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}
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/*
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* given a pointer into a directory item, delete it. This
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* handles items that have more than one entry in them.
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*/
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int btrfs_delete_one_dir_name(struct btrfs_trans_handle *trans,
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struct btrfs_root *root,
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struct btrfs_path *path,
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struct btrfs_dir_item *di)
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{
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struct extent_buffer *leaf;
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u32 sub_item_len;
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u32 item_len;
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int ret = 0;
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leaf = path->nodes[0];
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sub_item_len = sizeof(*di) + btrfs_dir_name_len(leaf, di) +
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btrfs_dir_data_len(leaf, di);
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item_len = btrfs_item_size_nr(leaf, path->slots[0]);
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if (sub_item_len == item_len) {
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ret = btrfs_del_item(trans, root, path);
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} else {
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/* MARKER */
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unsigned long ptr = (unsigned long)di;
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unsigned long start;
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start = btrfs_item_ptr_offset(leaf, path->slots[0]);
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memmove_extent_buffer(leaf, ptr, ptr + sub_item_len,
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item_len - (ptr + sub_item_len - start));
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btrfs_truncate_item(root, path, item_len - sub_item_len, 1);
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}
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return ret;
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}
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int verify_dir_item(struct btrfs_root *root,
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struct extent_buffer *leaf,
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struct btrfs_dir_item *dir_item)
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{
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u16 namelen = BTRFS_NAME_LEN;
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u8 type = btrfs_dir_type(leaf, dir_item);
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if (type >= BTRFS_FT_MAX) {
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btrfs_crit(root->fs_info, "invalid dir item type: %d",
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(int)type);
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return 1;
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}
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if (type == BTRFS_FT_XATTR)
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namelen = XATTR_NAME_MAX;
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if (btrfs_dir_name_len(leaf, dir_item) > namelen) {
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btrfs_crit(root->fs_info, "invalid dir item name len: %u",
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(unsigned)btrfs_dir_data_len(leaf, dir_item));
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return 1;
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}
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|
|
/* 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;
|
|
}
|