Re: [Qemu-devel] [PATCH v8 3/7] block: allow not one child for implicit node

[Max Reitz <mreitz@redhat.com>]

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On 29.05.19 17:46, Vladimir Sementsov-Ogievskiy wrote:
> Upcoming backup-top filter wants to operate like usual implicit filter
> node with fall-through to backing child. But also needs additional
> target child, let's support that.
> 
> On the other hand, after backup completion (before job dismiss) filter
> is still attached to job blk, but don't have any children. Support this
> too.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 57216f4115..3f4de3ae32 100644
> --- a/block.c
> +++ b/block.c
> @@ -6200,9 +6200,20 @@ void bdrv_refresh_filename(BlockDriverState *bs)
>      }
>  
>      if (bs->implicit) {
> -        /* For implicit nodes, just copy everything from the single child */
> +        /*
> +         * For implicit nodes, just copy everything from the single child or
> +         * from backing, if there are several children.
> +         * If there are no children for some reason (filter is still attached
> +         * to block-job blk, but already removed from backing chain of device)
> +         * do nothing.
> +         */
>          child = QLIST_FIRST(&bs->children);
> -        assert(QLIST_NEXT(child, next) == NULL);
> +        if (!child) {
> +            return;
> +        } else if (QLIST_NEXT(child, next)) {
> +            assert(bs->backing);
> +            child = bs->backing;
> +        }
>  
>          pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
>                  child->bs->exact_filename);

Reviewed-by: Max Reitz <mreitz@redhat.com>

(To be changed to bdrv_filtered_rw_bs(), of course)


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