bcachefs: Improve snapshots_seen

This makes the snapshots_seen data structure fsck private and improves
it; we now also track the equivalence class for each snapshot id we've
seen, which means we can detect when snapshot deletion hasn't finished
or run correctly (which will otherwise confuse fsck).

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
2 files changed