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Commit ef761cce authored by Filipe Manana's avatar Filipe Manana Committed by Greg Kroah-Hartman
Browse files

btrfs: propagate last_unlink_trans earlier when doing a rmdir 



[ Upstream commit c466e33e729a0ee017d10d919cba18f503853c60 ]

In case the removed directory had a snapshot that was deleted, we are
propagating its inode's last_unlink_trans to the parent directory after
we removed the entry from the parent directory. This leaves a small race
window where someone can log the parent directory after we removed the
entry and before we updated last_unlink_trans, and as a result if we ever
try to replay such a log tree, we will fail since we will attempt to
remove a snapshot during log replay, which is currently not possible and
results in the log replay (and mount) to fail. This is the type of failure
described in commit 1ec9a1ae ("Btrfs: fix unreplayable log after
snapshot delete + parent dir fsync").

So fix this by propagating the last_unlink_trans to the parent directory
before we remove the entry from it.

Fixes: 44f714da ("Btrfs: improve performance on fsync against new inode after rename/unlink")
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent c6f8ded6

fs/btrfs/inode.c

+18 −18
Original line number Diff line number Diff line
@@ -4747,7 +4747,6 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry) 
	int err = 0;

	struct btrfs_root *root = BTRFS_I(dir)->root;

	struct btrfs_trans_handle *trans;

	u64 last_unlink_trans;



	if (inode->i_size > BTRFS_EMPTY_DIR_SIZE)

		return -ENOTEMPTY;
@@ -4758,6 +4757,23 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry) 
	if (IS_ERR(trans))

		return PTR_ERR(trans);



	/*

	 * Propagate the last_unlink_trans value of the deleted dir to its

	 * parent directory. This is to prevent an unrecoverable log tree in the

	 * case we do something like this:

	 * 1) create dir foo

	 * 2) create snapshot under dir foo

	 * 3) delete the snapshot

	 * 4) rmdir foo

	 * 5) mkdir foo

	 * 6) fsync foo or some file inside foo

	 *

	 * This is because we can't unlink other roots when replaying the dir

	 * deletes for directory foo.

	 */

	if (BTRFS_I(inode)->last_unlink_trans >= trans->transid)

		BTRFS_I(dir)->last_unlink_trans = BTRFS_I(inode)->last_unlink_trans;



	if (unlikely(btrfs_ino(BTRFS_I(inode)) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {

		err = btrfs_unlink_subvol(trans, dir, dentry);

		goto out;
@@ -4767,28 +4783,12 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry) 
	if (err)

		goto out;



	last_unlink_trans = BTRFS_I(inode)->last_unlink_trans;



	/* now the directory is empty */

	err = btrfs_unlink_inode(trans, root, BTRFS_I(dir),

			BTRFS_I(d_inode(dentry)), dentry->d_name.name,

			dentry->d_name.len);

	if (!err) {

	if (!err)

		btrfs_i_size_write(BTRFS_I(inode), 0);

		/*

		 * Propagate the last_unlink_trans value of the deleted dir to

		 * its parent directory. This is to prevent an unrecoverable

		 * log tree in the case we do something like this:

		 * 1) create dir foo

		 * 2) create snapshot under dir foo

		 * 3) delete the snapshot

		 * 4) rmdir foo

		 * 5) mkdir foo

		 * 6) fsync foo or some file inside foo

		 */

		if (last_unlink_trans >= trans->transid)

			BTRFS_I(dir)->last_unlink_trans = last_unlink_trans;

	}

out:

	btrfs_end_transaction(trans);

	btrfs_btree_balance_dirty(root->fs_info);