yeah, seems my grep was wrong:
root@proxmox:~# mount | grep lxc
lxcfs on /var/lib/lxcfs type fuse.lxcfs (rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other)
root@proxmox:~# pct mount 201
mounted CT 201 in '/var/lib/lxc/201/rootfs'
root@proxmox:~# mount | grep lxc
lxcfs on /var/lib/lxcfs type fuse.lxcfs (rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other)
local-VMs/subvol-201-disk-0 on /var/lib/lxc/201/rootfs type zfs (rw,xattr,posixacl)
data1 on /var/lib/lxc/201/rootfs/mnt/data1 type zfs (rw,noatime,xattr,noacl)
data2 on /var/lib/lxc/201/rootfs/mnt/data2 type zfs (rw,xattr,noacl)
But fstrim -av onlytrims my nvme-ssd:
root@proxmox:~# fstrim -av
/boot/efi: 510.7 MiB (535486464 bytes) trimmed on /dev/nvme0n1p2
/: 8.8 GiB (9432932352 bytes) trimmed on /dev/mapper/pve-root
If I specify it directly:
root@proxmox:~# fstrim -v /var/lib/lxc/201/rootfs
fstrim: /var/lib/lxc/201/rootfs: the discard operation is not supported