How to check what is using a logical volume?

Maybe there is a better way to do what I am trying to achieve, so let me describe the whole problem. My / and /home directories are on a separate LV. It happened so the / LV get out of space. I then backup my /home and try to remove it to be able to resize /. However, when I did login to root tty and try to umount the /home with lvchange -a n /dev/trixxxy-vg/home I get prompt that this logical volume is in use. Logical volume trixxxy-vg/home contains a filesystem in use. My .emacs.d and .bashrc directories in /root were links to /home/user/ relevant, so I thought that can cause the problem, but after removing them nothing have changed. I guess there is a way, that I am not aware of, to check what file is currently using the particular logical volume. Or may one force remove such partition?