+static char *strdup_or_null(const char *s)
+{
+ if (!s)
+ return NULL;
+ return strdup(s);
+}
+
+int btrfs_get_toplevel_subvol(int fd, struct root_info *the_ri)
+{
+ int ret;
+ struct root_lookup rl;
+ struct rb_node *rbn;
+ struct root_info *ri;
+ u64 root_id;
+
+ ret = btrfs_list_get_path_rootid(fd, &root_id);
+ if (ret)
+ return ret;
+
+ ret = btrfs_list_subvols(fd, &rl);
+ if (ret)
+ return ret;
+
+ rbn = rb_first(&rl.root);
+ ri = rb_entry(rbn, struct root_info, rb_node);
+
+ if (ri->root_id != BTRFS_FS_TREE_OBJECTID)
+ return -ENOENT;
+
+ memcpy(the_ri, ri, offsetof(struct root_info, path));
+ the_ri->path = strdup_or_null("/");
+ the_ri->name = strdup_or_null("<FS_TREE>");
+ the_ri->full_path = strdup_or_null("/");
+ rb_free_nodes(&rl.root, free_root_info);
+
+ return ret;
+}
+
+int btrfs_get_subvol(int fd, struct root_info *the_ri)
+{
+ int ret, rr;
+ struct root_lookup rl;
+ struct rb_node *rbn;
+ struct root_info *ri;
+ u64 root_id;
+
+ ret = btrfs_list_get_path_rootid(fd, &root_id);
+ if (ret)
+ return ret;
+
+ ret = btrfs_list_subvols(fd, &rl);
+ if (ret)
+ return ret;
+
+ rbn = rb_first(&rl.root);
+ while(rbn) {
+ ri = rb_entry(rbn, struct root_info, rb_node);
+ rr = resolve_root(&rl, ri, root_id);
+ if (rr == -ENOENT) {
+ ret = -ENOENT;
+ rbn = rb_next(rbn);
+ continue;
+ }
+
+ if (!comp_entry_with_rootid(the_ri, ri, 0) ||
+ !uuid_compare(the_ri->uuid, ri->uuid)) {
+ memcpy(the_ri, ri, offsetof(struct root_info, path));
+ the_ri->path = strdup_or_null(ri->path);
+ the_ri->name = strdup_or_null(ri->name);
+ the_ri->full_path = strdup_or_null(ri->full_path);
+ ret = 0;
+ break;
+ }
+ rbn = rb_next(rbn);
+ }
+ rb_free_nodes(&rl.root, free_root_info);
+ return ret;
+}
+