On 30.07.19 16:18, Vladimir Sementsov-Ogievskiy wrote:
> Similarly to previous commit, prepare for parallelizing write-loop
> iterations.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/qcow2.c | 150 +++++++++++++++++++++++++++++---------------------
>  1 file changed, 88 insertions(+), 62 deletions(-)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 7fa71968b2..37766b8b7c 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c

[...]

> @@ -2283,62 +2362,11 @@ static coroutine_fn int qcow2_co_pwritev_part(

[...]

> +        ret = qcow2_co_pwritev_task(bs, cluster_offset, offset, cur_bytes,
> +                                    qiov, bytes_done, l2meta);

You’re passing bytes_done as qiov_offset here.  That is initialized to
0, so it ignores the qiov_offset given to qcow2_co_pwritev_part().

Max