As I understand it, you can lose both versions in #2. The rename drops the refcount of the old file to 0, freeing its inode and associated file blocks. If you'r

As I understand it, you can lose both versions in #2. The rename drops the refcount of the old file to 0, freeing its inode and associated file blocks. If you're lucky, they haven't been overwritten and can still find them. Not easily from an app though. On the other hand, the new file might not have been flushed to disk yet. I suspect this could be solved fs-side using a journal that doesn't just store metadata (as most do) but also file content. Slow, though, as files are effectively written to disk twice.