However, it would be nice to remove can_write_zeroes_with_unmap from
BlockDriverInfo, and make bdrv_can_write_zeroes_with_unmap just return
!!(bs->supported_zero_flags & BDRV_REQ_MAY_UNMAP). Kevin, what do you
think?
Actually, I may even just give a shot at writing this alternative patch,
to make Kevin's decision easier.
But actually qcow2 performs some checks for version inside get_info
callback before setting can_write_zeroes_with_unmap flag,
so we can't take into account such checks in
bdrv_can_write_zeroes_with_unmap subroutine. Therefore, I don't think it
is possible to do it like that.