+static int bch2_fs_initialize_subvolumes(struct bch_fs *c)
+{
+ struct bkey_i_snapshot root_snapshot;
+ struct bkey_i_subvolume root_volume;
+ int ret;
+
+ bkey_snapshot_init(&root_snapshot.k_i);
+ root_snapshot.k.p.offset = U32_MAX;
+ root_snapshot.v.flags = 0;
+ root_snapshot.v.parent = 0;
+ root_snapshot.v.subvol = BCACHEFS_ROOT_SUBVOL;
+ root_snapshot.v.pad = 0;
+ SET_BCH_SNAPSHOT_SUBVOL(&root_snapshot.v, true);
+
+ ret = bch2_btree_insert(c, BTREE_ID_snapshots,
+ &root_snapshot.k_i,
+ NULL, NULL, 0);
+ if (ret)
+ return ret;
+
+
+ bkey_subvolume_init(&root_volume.k_i);
+ root_volume.k.p.offset = BCACHEFS_ROOT_SUBVOL;
+ root_volume.v.flags = 0;
+ root_volume.v.snapshot = cpu_to_le32(U32_MAX);
+ root_volume.v.inode = cpu_to_le64(BCACHEFS_ROOT_INO);
+
+ ret = bch2_btree_insert(c, BTREE_ID_subvolumes,
+ &root_volume.k_i,
+ NULL, NULL, 0);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
+static int bch2_fs_upgrade_for_subvolumes(struct btree_trans *trans)
+{
+ struct bch_fs *c = trans->c;
+ struct btree_iter iter;
+ struct bkey_s_c k;
+ struct bch_inode_unpacked inode;
+ struct bkey_inode_buf *packed;
+ int ret;
+
+ bch2_trans_iter_init(trans, &iter, BTREE_ID_inodes,
+ POS(0, BCACHEFS_ROOT_INO), 0);
+ k = bch2_btree_iter_peek_slot(&iter);
+ ret = bkey_err(k);
+ if (ret)
+ goto err;
+
+ if (k.k->type != KEY_TYPE_inode) {
+ bch_err(c, "root inode not found");
+ ret = -ENOENT;
+ goto err;
+ }
+
+ ret = bch2_inode_unpack(bkey_s_c_to_inode(k), &inode);
+ BUG_ON(ret);
+
+ inode.bi_subvol = BCACHEFS_ROOT_SUBVOL;
+
+ packed = bch2_trans_kmalloc(trans, sizeof(*packed));
+ ret = PTR_ERR_OR_ZERO(packed);
+ if (ret)
+ goto err;
+
+ bch2_inode_pack(c, packed, &inode);
+ ret = bch2_trans_update(trans, &iter, &packed->inode.k_i, 0);
+err:
+ bch2_trans_iter_exit(trans, &iter);
+ return ret;
+}
+