[libvirt-users] external snapshots freezes block device since qemu 2.8

Hello there. I discovered, that since qemu 2.8 , external snapshots (very similar to: http://wiki.libvirt.org/page/Live-disk-backup-with-active-blockcommit), freezes block device after: # virsh blockcommit (...) There is no error message after completion of the command above. I'm using gluster + ZFS fuse mount as a storage for a VM on gentoo. libvirt debug showed nothing helpful. With qemu <2.8 -: snapshots are working as expected. Is this a known issue? Is it qemu or libvirt ? If it helps, how can i diagnose this further? Thank You & Best regards Piotr Rybicki