From: Filipe Manana Date: Sat, 12 Jul 2025 04:45:48 +0000 (-0400) Subject: btrfs: propagate last_unlink_trans earlier when doing a rmdir X-Git-Tag: v6.1.146~44 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=72be0d6b305a115c3fd80cbfaff206658cc9f43b;p=thirdparty%2Fkernel%2Fstable.git 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 1ec9a1ae1e30 ("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: 44f714dae50a ("Btrfs: improve performance on fsync against new inode after rename/unlink") Reviewed-by: Johannes Thumshirn Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 5ecc2f3dc3a99..469a622b440b6 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -4881,6 +4881,23 @@ 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)) { err = btrfs_unlink_subvol(trans, dir, dentry); goto out; @@ -4895,17 +4912,6 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry) &fname.disk_name); 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 (BTRFS_I(inode)->last_unlink_trans >= trans->transid) btrfs_record_snapshot_destroy(trans, BTRFS_I(dir)); }