I failed to reproduce the issue on s390x Fedora Rawhide, Linux kernel 5.5.0-0.rc4.git2.1.fc32.s390x, glibc-2.30.9000-31.fc32.s390x.

I tested filesystem nfs and tmpfs.

test_add_file_after_2107() pass.

[vstinner@devel10 ~]$ uname -r
5.5.0-0.rc4.git2.1.fc32.s390x

[vstinner@devel10 ~]$ rpm -q glibc
glibc-2.30.9000-31.fc32.s390x

[vstinner@devel10 ~]$ strace -o trace ./mtime
uname -a:
Linux devel10.s390.bos.redhat.com 5.5.0-0.rc4.git2.1.fc32.s390x #1 SMP Fri Jan 3 20:19:26 UTC 2020 s390x s390x s390x GNU/Linux
sizeof(time_t) = 8 bytes
sizeof(void*) = 8 bytes

open(testfn, O_WRONLY | O_CREAT)
utimensat(AT_FDCWD, testfn, {atime=mtime=4386268800.0}, 0)
stat(testfn)
st.st_mtime = 4386268800
st.st_mtim.tv_nsec = 0
(ignored: st.st_mtime.tv_sec = 0)
unlink(testfn)

[vstinner@devel10 ~]$ grep -E '^(utime|stat)' trace 
utimensat(AT_FDCWD, "testfn", [{tv_sec=4386268800, tv_nsec=0} /* 2108-12-29T19:00:00-0500 */, {tv_sec=4386268800, tv_nsec=0} /* 2108-12-29T19:00:00-0500 */], 0) = 0
stat("testfn", {st_mode=S_IFREG|041, st_size=0, ...}) = 0