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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 1ec9a1ae1e ("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: 44f714dae5 ("Btrfs: improve performance on fsync against new inode after rename/unlink")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit d77a16802896bcc0cbe66facf87d7af57262ea1a)
This commit is contained in:
Filipe Manana 2025-06-20 15:54:05 +01:00 committed by Wentao Guan
parent b0f4ec74dc
commit 2dbd663f91
1 changed files with 18 additions and 18 deletions
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36
fs/btrfs/inode.c
View File

@ -4617,7 +4617,6 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
int ret = 0;
struct btrfs_trans_handle *trans;
u64 last_unlink_trans;
struct fscrypt_name fname;
if (inode->i_size > BTRFS_EMPTY_DIR_SIZE)
@ -4643,6 +4642,23 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
goto out_notrans;
}
/*
* 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)) {
ret = btrfs_unlink_subvol(trans, BTRFS_I(dir), dentry);
goto out;
@ -4652,27 +4668,11 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
if (ret)
goto out;
last_unlink_trans = BTRFS_I(inode)->last_unlink_trans;
/* now the directory is empty */
ret = btrfs_unlink_inode(trans, BTRFS_I(dir), BTRFS_I(d_inode(dentry)),
&fname.disk_name);
if (!ret) {
if (!ret)
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);
out_notrans: