On 05/31/2016 03:15 AM, Denis V. Lunev wrote:
> From: Pavel Butsykin <pbutsykin@virtuozzo.com>
> 
> Added implementation of the qcow2_co_write_compressed function that
> will allow us to safely use compressed writes for the qcow2 from running VMs.
> 
> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Jeff Cody <jcody@redhat.com>
> CC: Markus Armbruster <armbru@redhat.com>
> CC: Eric Blake <eblake@redhat.com>
> CC: John Snow <jsnow@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qcow2.c | 89 ++++++++++++++++++++++++++++++++++-------------------------
>  1 file changed, 52 insertions(+), 37 deletions(-)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index c9306a7..38caa66 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2535,13 +2535,16 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset)
>  
>  /* XXX: put compressed sectors first, then all the cluster aligned
>     tables to avoid losing bytes in alignment */
> -static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num,
> -                                  const uint8_t *buf, int nb_sectors)
> +static coroutine_fn int
> +qcow2_co_write_compressed(BlockDriverState *bs, int64_t sector_num,
> +                          int nb_sectors, QEMUIOVector *qiov)

Is it worth converting to a byte-based qcow2_co_pwrite_compressed()
while at it?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org