Il 24/02/2014 12:33, Fam Zheng ha scritto:
> This is (or should be) bdrv_co_write_zeroes without BDRV_REQ_MAY_UNMAP.
But IIUC bdrv_co_write_zeroes without BDRV_REQ_MAY_UNMAP doesn't require
cluster allocation if it's allocated yet, which is a bit different.
Yeah, that's why I wrote "or should be". Those are the intended
semantics of bdrv_co_write_zeroes without BDRV_REQ_MAY_UNMAP: always
allocate a cluster that will read as zeroes (allocating even if it does
not necessarily write the zeroes).
For legacy reasons it may not be exactly what is implemented. I asked
Kevin a couple of weeks ago and he sent a patch, but even he wasn't sure
of what qcow2 was doing util he looked at the code. :)
Paolo
