[$] The Btrfs inode-number epic (part 1: the problem)
Unix-like systems — and their users — tend to expect all filesystems to
behave in the same way. But those users are also often interested in fancy
new filesystems offering features that were never envisioned by the
developers of the Unix filesystem model; that has led to a number of
interesting incompatibilities over time. Btrfs is certainly one of those
filesystems; it provides a long list of features that are found in few
other systems, and some of those features interact poorly with the
traditional view of how filesystems work. Recently, Neil Brown has been
trying to resolve a specific source of confusion relating to how Btrfs
handles inode numbers.