Commit c1621871 authored by Omar Sandoval's avatar Omar Sandoval Committed by David Sterba
Browse files

btrfs: reserve correct number of items for rename 



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: default avatarSweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent bca4ad7c

fs/btrfs/inode.c

+68 −20
Original line number Diff line number Diff line
@@ -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);

		/*

	 * 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).

	 */

	trans_num_items = 11;

		 * 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;

	}

	/*

	 * 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 += 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);