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btrfs: reserve correct number of items for rename

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btrfs_rename() and btrfs_rename_exchange() don't account for enough
items. Replace the incorrect explanations with a specific breakdown of
the number of items and account them accurately.

Note that this glosses over RENAME_WHITEOUT because the next commit is
going to rework that, too.

Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Omar Sandoval 2022-03-09 17:31:32 -08:00 committed by David Sterba
parent bca4ad7c0b
commit c162187143
1 changed files with 67 additions and 19 deletions
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86
fs/btrfs/inode.c
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@ -9051,6 +9051,7 @@ static int btrfs_rename_exchange(struct inode *old_dir,
{
struct btrfs_fs_info *fs_info = btrfs_sb(old_dir->i_sb);
struct btrfs_trans_handle *trans;
unsigned int trans_num_items;
struct btrfs_root *root = BTRFS_I(old_dir)->root;
struct btrfs_root *dest = BTRFS_I(new_dir)->root;
struct inode *new_inode = new_dentry->d_inode;
@ -9082,14 +9083,37 @@ static int btrfs_rename_exchange(struct inode *old_dir,
down_read(&fs_info->subvol_sem);
/*
* We want to reserve the absolute worst case amount of items. So if
* both inodes are subvols and we need to unlink them then that would
* require 4 item modifications, but if they are both normal inodes it
* would require 5 item modifications, so we'll assume their normal
* inodes. So 5 * 2 is 10, plus 2 for the new links, so 12 total items
* should cover the worst case number of items we'll modify.
* For each inode:
* 1 to remove old dir item
* 1 to remove old dir index
* 1 to add new dir item
* 1 to add new dir index
* 1 to update parent inode
*
* If the parents are the same, we only need to account for one
*/
trans = btrfs_start_transaction(root, 12);
trans_num_items = (old_dir == new_dir ? 9 : 10);
if (old_ino == BTRFS_FIRST_FREE_OBJECTID) {
/*
* 1 to remove old root ref
* 1 to remove old root backref
* 1 to add new root ref
* 1 to add new root backref
*/
trans_num_items += 4;
} else {
/*
* 1 to update inode item
* 1 to remove old inode ref
* 1 to add new inode ref
*/
trans_num_items += 3;
}
if (new_ino == BTRFS_FIRST_FREE_OBJECTID)
trans_num_items += 4;
else
trans_num_items += 3;
trans = btrfs_start_transaction(root, trans_num_items);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
goto out_notrans;
@ -9368,21 +9392,45 @@ static int btrfs_rename(struct user_namespace *mnt_userns,
if (new_inode && S_ISREG(old_inode->i_mode) && new_inode->i_size)
filemap_flush(old_inode->i_mapping);
/* close the racy window with snapshot create/destroy ioctl */
if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
if (old_ino == BTRFS_FIRST_FREE_OBJECTID) {
/* Close the race window with snapshot create/destroy ioctl */
down_read(&fs_info->subvol_sem);
/*
* 1 to remove old root ref
* 1 to remove old root backref
* 1 to add new root ref
* 1 to add new root backref
*/
trans_num_items = 4;
} else {
/*
* 1 to update inode
* 1 to remove old inode ref
* 1 to add new inode ref
*/
trans_num_items = 3;
}
/*
* We want to reserve the absolute worst case amount of items. So if
* both inodes are subvols and we need to unlink them then that would
* require 4 item modifications, but if they are both normal inodes it
* would require 5 item modifications, so we'll assume they are normal
* inodes. So 5 * 2 is 10, plus 1 for the new link, so 11 total items
* should cover the worst case number of items we'll modify.
* If our rename has the whiteout flag, we need more 5 units for the
* new inode (1 inode item, 1 inode ref, 2 dir items and 1 xattr item
* when selinux is enabled).
* 1 to remove old dir item
* 1 to remove old dir index
* 1 to update old parent inode
* 1 to add new dir item
* 1 to add new dir index
* 1 to update new parent inode (if it's not the same as the old parent)
*/
trans_num_items = 11;
trans_num_items += 6;
if (new_dir != old_dir)
trans_num_items++;
if (new_inode) {
/*
* 1 to update inode
* 1 to remove inode ref
* 1 to remove dir item
* 1 to remove dir index
* 1 to possibly add orphan item
*/
trans_num_items += 5;
}
if (flags & RENAME_WHITEOUT)
trans_num_items += 5;
trans = btrfs_start_transaction(root, trans_num_items);