btrfs_drop_snapshot
int btrfs_drop_snapshot(struct btrfs_root *root, bool update_ref, bool for_reloc);
ret2 = btrfs_drop_snapshot(reloc_root, false, true);
ret2 = btrfs_drop_snapshot(root, false, true);
ret = btrfs_drop_snapshot(root, false, false);
ret = btrfs_drop_snapshot(root, true, false);