I can't find a simple, straight answer about which filesystem metadata operations are actually persisted to the ext4 & xfs filesystem journals. Note that I am not inquiring about what POSIX declares to be "atomic". I'm more concerned about what subset of atomic filesystem operations are effectively durable by virtue of running with a journal enabled without having to bend over backwards and
fsync(2) all the time.
Operations I'm fairly certain count:
Operations I'm not entirely sure about:
symlink(2) case is the most troubling, since there does not seem to be any straightforward way to
fdatasync(2) the underlying datablocks that store the content of a symlink. Knowing that the journal takes care of this for me would be a relief.