I have a Linux system (Opensuse leap, but it's not that important) installed on a logical volume (and the ext4 filesystem). I want to upgrade it to a newer version, but to be on the safe side, I want to create an LVM snapshot first in case something goes wrong.
My current LV does not have enough capacity to hold both the old version of the file system (on a snapshot) and the new version (after upgrade): the LV has 12GB, the files take 8 GB leaving 4 GB free. I can temporarily extend the LV to, say, 20 GB. Now: do I have to extend the filesystem to 20GB as well or can LVM leverage the space which is not allocated for the filesystem?