From 9ffa9f42dd630e01a507905b60cc7f45d8326327 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 30 Nov 2017 16:17:47 +0100
Subject: [PATCH 08/36] block: don't add 'driver' to options when referring to
 backing via node name

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20171130161747.18388-2-kwolf@redhat.com>
Patchwork-id: 78023
O-Subject: [RHV-7.5 qemu-kvm-rhev PATCH 1/1] block: don't add 'driver' to options when referring to backing via node name
Bugzilla: 1505701
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: John Snow <jsnow@redhat.com>

From: Peter Krempa <pkrempa@redhat.com>

When referring to a backing file of an image via node name
bdrv_open_backing_file would add the 'driver' option to the option list
filling it with the backing format driver. This breaks construction of
the backing chain via -blockdev, as bdrv_open_inherit reports an error
if both 'reference' and 'options' are provided.

$ qemu-img create -f raw /tmp/backing.raw 64M
$ qemu-img create -f qcow2 -F raw -b /tmp/backing.raw /tmp/test.qcow2
$ qemu-system-x86_64 \
  -blockdev driver=file,filename=/tmp/backing.raw,node-name=backing \
  -blockdev driver=qcow2,file.driver=file,file.filename=/tmp/test.qcow2,node-name=root,backing=backing
qemu-system-x86_64: -blockdev driver=qcow2,file.driver=file,file.filename=/tmp/test.qcow2,node-name=root,backing=backing: Could not open backing file: Cannot reference an existing block device with additional options or a new filename

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 6bff597bf6580ecc691258e849f652911dbdda7c)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block.c b/block.c
index 3308814..6fb4e98 100644
--- a/block.c
+++ b/block.c
@@ -2178,7 +2178,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
         goto free_exit;
     }
 
-    if (bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) {
+    if (!reference &&
+        bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) {
         qdict_put_str(options, "driver", bs->backing_format);
     }
 
-- 
1.8.3.1