tree 4424cbe0276ababf64cd21535e705e124d51bd66
parent 51e84d3bbff55f5ac79fef0d1bbf515d6d397289
author Kent Overstreet <kent.overstreet@linux.dev> 1680103132 -0400
committer Kent Overstreet <kent.overstreet@linux.dev> 1698009001 -0400

bcachefs: BTREE_ID_snapshot_tree

This adds a new btree which gets us a persistent per-snapshot-tree
identifier.

 - BTREE_ID_snapshot_trees
 - KEY_TYPE_snapshot_tree
 - bch_snapshot now has a field that points to a snapshot_tree

This is going to be used to designate one snapshot ID/subvolume out of a
given tree of snapshots as the "main" subvolume, so that we can do quota
accounting in that subvolume and not the rest.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>