05.04.2019 19:56, Andrey Shinkevich wrote:
> The bottom node is the intermediate block device that has the base as its
> backing image. It is used instead of the base node while a block stream
> job is running to avoid dependency on the base that may change due to the
> parallel jobs. The change may take place due to a filter node as well that
> is inserted between the base and the intermediate bottom node. It occurs
> when the base node is the top one for another commit or stream job.
> After the introduction of the bottom node, don't freeze its backing child,
> that's the base, anymore.
>
> Suggested-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> Signed-off-by: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> ---
> block/stream.c | 56
> +++++++++++++++++++++++++++-----------------------
> block/trace-events | 2 +-
> tests/qemu-iotests/245 | 4 ++--
> 3 files changed, 33 insertions(+), 29 deletions(-)
>
[..]
> @@ -232,8 +232,13 @@ void stream_start(const char *job_id, BlockDriverState
> *bs,
> StreamBlockJob *s;
> BlockDriverState *iter;
> bool bs_read_only;
> + BlockDriverState *bottom = NULL;
Why to set NULL? you can set to bdrv_find_overlay() here.
> + int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
> +
> + /* Find the bottom node that has the base as its backing image */
I don't think we need comment, as it's exactly what bdrv_find_overly does.
> + bottom = bdrv_find_overlay(bs, base);
>
> - if (bdrv_freeze_backing_chain(bs, base, errp) < 0) {
> + if (bdrv_freeze_backing_chain(bs, bottom, errp) < 0) {
> return;
> }
>
--
Best regards,
Vladimir
