4 How Directory Committing Works:
7 version - current version of directory
8 committing_version - which version was sent to stable storage
9 last_committed_version - last version to be safely stored
12 parent_dir_version - what dir version i was in when i was dirtied. (*)
14 (*) note that if you change an inode, mark_dirty() again, even if it's already dirty!
19 A call to commit_dir(dir, context) will ensure tha the _current_ version is stored safely on disk before the context is finished.
21 When a commit completes, inodes in the directory are checked. If they are dirty and belonged to the _committed_ (or earlier) version, then they are marked clean. If they belong to a newer version, then they are _still dirty_.