Signed-off-by: Peter Krempa <pkrempa@redhat.com>
---
 docs/news.xml | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/docs/news.xml b/docs/news.xml
index 7fd88f9998..92103ec308 100644
--- a/docs/news.xml
+++ b/docs/news.xml
@@ -48,6 +48,23 @@
     <section title="Improvements">
     </section>
     <section title="Bug fixes">
+      <change>
+        <summary>
+          qemu: Open backing chain late for shallow block copy reusing external images
+        </summary>
+        <description>
+          With introduction of -blockdev specification of storage for qemu VMs
+          in libvirt-5.10 we've started opening the backing chain of the
+          destination/mirror of a virDomainBlockcopy started with
+          VIR_DOMAIN_BLOCK_COPY_REUSE_EXT | VIR_DOMAIN_BLOCK_COPY_SHALLOW flags
+          when starting the job rather than when virDomainBlockJobAbort with
+          VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT is issued. For users depending on
+          this undocumented quirk this caused a regression in behaviour as
+          the backing chain could not be modified while the copy of the top
+          image was progressing. Note that this fix also requires qemu-5.0 while
+          -blockdev is used starting from qemu-4.2.
+        </description>
+      </change>
     </section>
   </release>
   <release version="v6.1.0" date="2020-03-03">
-- 
2.24.1

On Fri, Mar 13, 2020 at 02:26:49PM +0100, Peter Krempa wrote:
> Signed-off-by: Peter Krempa <pkrempa@redhat.com>
> ---
>  docs/news.xml | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/docs/news.xml b/docs/news.xml
> index 7fd88f9998..92103ec308 100644
> --- a/docs/news.xml
> +++ b/docs/news.xml
> @@ -48,6 +48,23 @@
>      <section title="Improvements">
>      </section>
>      <section title="Bug fixes">
> +      <change>
> +        <summary>
> +          qemu: Open backing chain late for shallow block copy reusing external images
> +        </summary>
> +        <description>
> +          With introduction of -blockdev specification of storage for qemu VMs

Nit: May I suggest: 

    "With introduction of -blockdev for QEMU storage configuration in
    libvirt-5.10, we've ..."

> +          in libvirt-5.10 we've started opening the backing chain of the
> +          destination/mirror of a virDomainBlockcopy started with
> +          VIR_DOMAIN_BLOCK_COPY_REUSE_EXT | VIR_DOMAIN_BLOCK_COPY_SHALLOW flags
> +          when starting the job rather than when virDomainBlockJobAbort with
> +          VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT is issued. For users depending on
> +          this undocumented quirk this caused a regression in behaviour as

Might want to highlight that the "undocumented quirk" is from
pre-blockdev world; we have to remember that users of the API do not
meditate on the Block Layer :-).  Maybe a hint like:

    "undocumented quirk" --> "undocumented quirk (which existed before -blockdev)"

> +          the backing chain could not be modified while the copy of the top
> +          image was progressing. Note that this fix also requires qemu-5.0 while
> +          -blockdev is used starting from qemu-4.2.

Also, ultra nit: s/qemu/QEMU/g

With the above addressed, FWIW:

Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>

-- 
/kashyap