Allow f2fs to reserve bytes for footer when formatting

            result = exec_cmd(e2fsdroid_argv[0], const_cast<char**>(e2fsdroid_argv));

          }

        } else {   /* Has to be f2fs because we checked earlier. */

            char *bytes_reserved = nullptr;

            char *num_sectors = nullptr;

            const char* f2fs_argv[6] = {"mkfs.f2fs", "-t1"};

            if (length < 0) {

                if (asprintf(&bytes_reserved, "%zd", -length) <= 0) {

                    LOG(ERROR) << "format_volume: failed to create " << v->fs_type

                               << " command for " << v->blk_device;

                    return -1;

                }

                f2fs_argv[2] = "-r";

                f2fs_argv[3] = bytes_reserved;

                f2fs_argv[4] = v->blk_device;

                f2fs_argv[5] = nullptr;

            } else {

                /* num_sectors can be zero which mean whole device space */

                if (length >= 512 && asprintf(&num_sectors, "%zd", length / 512) <= 0) {

                    LOG(ERROR) << "format_volume: failed to create " << v->fs_type

                               << " command for " << v->blk_device;

                    return -1;

                }

                snprintf(num_sectors, sizeof(num_sectors), "%zd", length / 512);

                f2fs_argv[2] = v->blk_device;

                f2fs_argv[3] = num_sectors;

                f2fs_argv[4] = nullptr;

            }

            const char *f2fs_path = "/sbin/mkfs.f2fs";

            const char* const f2fs_argv[] = {"mkfs.f2fs", "-t", "-d1", v->blk_device, num_sectors, nullptr};

            result = exec_cmd(f2fs_path, (char* const*)f2fs_argv);

            free(num_sectors);

            free(bytes_reserved);

        }

        if (result != 0) {

            PLOG(ERROR) << "format_volume: make " << v->fs_type << " failed on " << v->blk_device;