On 02/02/2018 05:15 PM, Eric Blake wrote:
On 02/02/2018 08:06 AM, Edgar Kaziakhmedov wrote:

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.
Here's the patch I proposed (it looks like I forgot to CC you):

https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg06471.html

Yes, it was possible to move check to open, ok, get it.

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