tail: unrecognized file system type 0x794c7630 for ‘/var/log/upstart/carbon_front.log’. please report this to bug-coreutils@gnu.org. reverting to polling

The relevant line from /proc/mounts:

overlay /var overlay rw,relatime,lowerdir=/home/alexey/.hola_containers/empty.lower,upperdir=/home/alexey/.hola_containers/mounts/zs-graphite/var.upper,workdir=/home/alexey/.hola_containers/mounts/zs-graphite/var.upper.work 0 0

Kernel 4.3.0. Don't confuse the filesystem with “overlayfs” available in older kernels.

I know from experiment that this filesystem does in fact need polling.