Can I override the SELinux file context of a file whose filesystem is mounted with the `context` mount option?

Issue

• A filesystem is mounted with the context=system_u:object_r:public_content_rw_t:s0 mount option. I want to change the context of certain files on the filesytsem to var_log_t. But when I change the context with semanage fcontext and then run restorecon, the context doesn't change.

# mount -o context=system_u:object_r:public_content_rw_t:s0 /dev/test_vg2/test_lv1 /mnt2
# touch /mnt2/testdir/testfile
# ls -Z /mnt2/testdir/
-rw-r--r--. root root system_u:object_r:public_content_rw_t:s0 testfile
# semanage fcontext -at var_log_t /mnt2/testdir/testfile 
# restorecon -Rv /mnt2/testdir/
# ls -Z /mnt2/testdir/
-rw-r--r--. root root system_u:object_r:public_content_rw_t:s0 testfile