Re: [Qemu-block] [PATCH v8 00/11] Support streaming to an intermediate layer

[Alberto Garcia]

On Wed 24 Jun 2015 10:02:03 AM CEST, Alberto Garcia wrote:

> [A] <- [B] <- [C] <- [D] <- [E] <- [F] <- [G]
>
> [...]
>
> The way it works is that stream_start() reopens the destination image
> in read-write mode (if needed), creates the stream_run() coroutine to
> copy the data, and finally stream_complete() puts it back in read-only
> mode and closes the images that are removed from the chain.

There's more. If I perform a single streaming operation [A] => [D] this
also crashes, although in a different way.

   block.c:1764: bdrv_reopen_prepare: Assertion `reopen_state->bs->drv != 
((void *)0)' failed.

What happens is that in stream_complete() all images that have been
removed from the chain ([A], [B] and [C]) are closed, and then [D] is
reopened in read-only mode.

The reopen queue contains [C], that is still listed as a child of [D]
although it's no longer a valid pointer.

[C] is opened using bdrv_open_backing_file() and attached to [D] with
bdrv_attach_child(), but never detached afterwards.

Berto