Method truncate

fs/subfs.cpp:194–198

            return underlayfs->access(path, mode);
        }
        virtual int truncate(const char *path, off_t length) override
        {
            PathCat __(this, path);
            return underlayfs->truncate(path, length);
        }
        virtual int syncfs() override
        {
            return underlayfs->syncfs();