Re: [PATCH v10 7/9] stream: skip filters when writing backing file name to QCOW2 header

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

29.09.2020 15:38, Andrey Shinkevich wrote:
> Avoid writing a filter JSON-name to QCOW2 image when the backing file
> is changed after the block stream job.
> 
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>   block/stream.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/block/stream.c b/block/stream.c
> index e0540ee..b0719e9 100644
> --- a/block/stream.c
> +++ b/block/stream.c
> @@ -65,6 +65,7 @@ static int stream_prepare(Job *job)
>       BlockDriverState *bs = blk_bs(bjob->blk);
>       BlockDriverState *unfiltered_bs = bdrv_skip_filters(bs);
>       BlockDriverState *base = bdrv_filter_or_cow_bs(s->above_base);
> +    BlockDriverState *base_metadata = bdrv_skip_filters(base);

Could we call it base_unfiltered in according with all such things?

>       Error *local_err = NULL;
>       int ret = 0;
>   
> @@ -73,10 +74,10 @@ static int stream_prepare(Job *job)
>   
>       if (bdrv_cow_child(unfiltered_bs)) {
>           const char *base_id = NULL, *base_fmt = NULL;
> -        if (base) {
> -            base_id = s->backing_file_str;

Seems backing_file_str becomes unused and we should drop it. So, actually,
this patch fix two problems:

  - do not save backing_file_str at stream start (as base may change during the job)
  - avoid json filters in final qcow2 image metadata

> -            if (base->drv) {
> -                base_fmt = base->drv->format_name;
> +        if (base_metadata) {
> +            base_id = base_metadata->filename;
> +            if (base_metadata->drv) {
> +                base_fmt = base_metadata->drv->format_name;
>               }
>           }
>           bdrv_set_backing_hd(unfiltered_bs, base, &local_err);
> 


-- 
Best regards,
Vladimir