kvm rbd driver (and maybe others, i.e. qcow2, qed and so on) does not report DISCARD-ZERO flag
This bug has been copied automatically from: https://bugs.launchpad.net/qemu/+bug/1652459
Reported by 'Коренберг Марк' on 2016-12-24 :
# lsblk -D NAME DISC-ALN DISC-GRAN DISC-MAX DISC-ZERO sda 0 4K 1G 0 ├─sda1 0 4K 1G 0 ├─sda2 1024 4K 1G 0 └─sda5 0 4K 1G 0 Last column should be `1` at least for "RBD+discard=unmap" since reading from discarded regions in RBD MUST return zeroes. The same with QCOW2, QED and sparse raw images. KVM should copy value of this flag when real raw device (i.e. real SSD) with discard capability is used as virtual disk.