Re: [Qemu-block] [PATCH 0/2] Update the inherits_from pointer after stream and commit

[Alberto Garcia]

ping

> Hi all,
>
> when you open an image [A] with a few more images on the backing chain
> you get something like this:
>
>     [E] <- [D] <- [C] <- [B] <- [A]
>
> Here you can go from [A] to [E] by following the bs->backing
> pointer. At the same time each one of the backing files has an
> 'inherits_from' attribute pointing to their parent, so you can go from
> [E] to [A] following the inherits_from pointer.
>
> 'inherits_from' is used on bdrv_reopen_queue_child() to decide if a
> node's children must be reopened together with the parent and inherit
> its options.
>
> If some the intermediate nodes are removed (either by block-stream or
> by block-commit) you end up with something like this:
>
>    [E] <- [A]
>
> In this case we would expect [E] to inherit from [A], however its
> inherits_from pointer is NULL and trying to change its options by
> reopening [A] with backing.option=value fails.
>
> This patch series fixes this. See each individual patch for more
> details.