[$] Snapshots, inodes, and filesystem identifiers

A longstanding problem with Btrfs subvolumes
and duplicate inode numbers was the topic of a late-breaking filesystem session
at the
2022 Linux Storage,
Filesystem, Memory-management and BPF Summit (LSFMM). The problem had
cropped up in the bcachefs session but
Josef Bacik deferred that discussion to this just-created session, which he led. The
problem is not limited to Btrfs, though, since filesystem snapshots for
other filesystems can
have similar kinds of problems.