What sort of data might BtrFS store in its BTrees?

There's inodes representing file metadata.

There's file contents, if the file's small enough its not worth storing elsewhere.

There's entries for looking up a file's ID in a directory by its filename's crc32c hash. Incidentally my hypothetical string-centric CPU includes hardwired circuitry for this.

There's references to where the file's stored on disk, with snapshotting & reference counting. Or groups thereof.

There's backreferences.

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