This is easy to confirm by code review:

[openxs@chief percona-5.6]$ grep -rn os_file_handle_error_cond_exit *
storage/innobase/os/os0file.cc:586:os_file_handle_error_cond_exit(
storage/innobase/os/os0file.cc:684:     return(os_file_handle_error_cond_exit(name, operation, TRUE, FALSE));
storage/innobase/os/os0file.cc:700:     return(os_file_handle_error_cond_exit(
[openxs@chief percona-5.6]$ vi +684 storage/innobase/os/os0file.cc
[openxs@chief percona-5.6]$ grep -rn os_file_handle_error *
storage/innobase/os/os0file.cc:586:os_file_handle_error_cond_exit(
storage/innobase/os/os0file.cc:678:os_file_handle_error(
storage/innobase/os/os0file.cc:684:     return(os_file_handle_error_cond_exit(name, operation, TRUE, FALSE));
storage/innobase/os/os0file.cc:692:os_file_handle_error_no_exit(
storage/innobase/os/os0file.cc:700:     return(os_file_handle_error_cond_exit(
storage/innobase/os/os0file.cc:841:                     os_file_handle_error(dirname, "opendir");
storage/innobase/os/os0file.cc:852:             os_file_handle_error(dirname, "opendir");
storage/innobase/os/os0file.cc:874:             os_file_handle_error_no_exit(NULL, "closedir", FALSE);
storage/innobase/os/os0file.cc:886:             os_file_handle_error_no_exit(NULL, "closedir", FALSE);
storage/innobase/os/os0file.cc:958:             os_file_handle_error_no_exit(NULL, "readdir_next_file", FALSE);
storage/innobase/os/os0file.cc:1044:            os_file_handle_error_no_exit(full_path, "stat", FALSE);
storage/innobase/os/os0file.cc:1094:            os_file_handle_error_no_exit(
storage/innobase/os/os0file.cc:1108:            os_file_handle_error_no_exit(pathname, "mkdir", FALSE);
storage/innobase/os/os0file.cc:1216:                    retry = os_file_handle_error(
storage/innobase/os/os0file.cc:1283:                    retry = os_file_handle_error(
storage/innobase/os/os0file.cc:1533:            os_file_handle_error_no_exit(name, "ioctl", FALSE);
storage/innobase/os/os0file.cc:1704:                            retry = os_file_handle_error_no_exit(
storage/innobase/os/os0file.cc:1707:                            retry = os_file_handle_error(name, operation);
storage/innobase/os/os0file.cc:1789:                            retry = os_file_handle_error_no_exit(
storage/innobase/os/os0file.cc:1792:                            retry = os_file_handle_error(name, operation);
storage/innobase/os/os0file.cc:1912:            os_file_handle_error_no_exit(name, "delete", FALSE);
storage/innobase/os/os0file.cc:1976:            os_file_handle_error_no_exit(name, "delete", FALSE);
storage/innobase/os/os0file.cc:2020:    os_file_handle_error_no_exit(oldpath, "rename", FALSE);
storage/innobase/os/os0file.cc:2029:            os_file_handle_error_no_exit(oldpath, "rename", FALSE);
storage/innobase/os/os0file.cc:2060:    os_file_handle_error(NULL, "close");
storage/innobase/os/os0file.cc:2069:            os_file_handle_error(NULL, "close");
storage/innobase/os/os0file.cc:2170:                    os_file_handle_error_no_exit (name, "posix_fallocate",
storage/innobase/os/os0file.cc:2360:    os_file_handle_error(NULL, "flush");
storage/innobase/os/os0file.cc:2414:    os_file_handle_error(NULL, "flush");
storage/innobase/os/os0file.cc:2820:    retry = os_file_handle_error(NULL, "read");
storage/innobase/os/os0file.cc:2943:    retry = os_file_handle_error_no_exit(NULL, "read", FALSE);
storage/innobase/os/os0file.cc:3192:            os_file_handle_error_no_exit(path, "stat", FALSE);
storage/innobase/os/os0file.cc:3220:            os_file_handle_error_no_exit(path, "stat", FALSE);
storage/innobase/os/os0file.cc:3269:            os_file_handle_error_no_exit(path, "stat", FALSE);
storage/innobase/os/os0file.cc:3322:            os_file_handle_error_no_exit(path, "stat", FALSE);
storage/innobase/os/os0file.cc:4874:    if (os_file_handle_error(
storage/innobase/os/os0file.cc:4990:    } else if (os_file_handle_error(slot->name, "Windows aio")) {
storage/innobase/os/os0file.cc:5324:            /* os_file_handle_error does tell us if we should retry
storage/innobase/os/os0file.cc:5331:            os_file_handle_error(slot->name, "Linux aio");

As we can see, in both cases when error is reported for "read" operation:

storage/innobase/os/os0file.cc:2820:    retry = os_file_handle_error(NULL, "read");
storage/innobase/os/os0file.cc:2943:    retry = os_file_handle_error_no_exit(NULL, "read", FALSE);

file name is passed as NULL, so it is reported as "(unknown)" in os0file.cc here (5.6 code is used):

    658                 if (should_exit || !on_error_silent) {
    659                         ib_logf(IB_LOG_LEVEL_ERROR, "File %s: '%s' returned OS "
    660                                 "error " ULINTPF ".%s", name ? name : "(unknown)",
    661                                 operation, err, should_exit
    662                                 ? " Cannot continue operation" : "");
    663                 }