From e59a0cf17b1b9932b65e6fc25d6856976f5e4831 Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Sat, 24 Feb 2018 16:40:32 +0100
Subject: block: Handle null backing link

Instead of converting all "backing": null instances into "backing": "",
handle a null value directly in bdrv_open_inherit().

This enables explicitly null backing links for json:{} filenames.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-Id: <20180224154033.29559-7-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: rebase to qobject_to() parameter order and qapi headers split]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
 tests/qemu-iotests/089     | 20 ++++++++++++++++++++
 tests/qemu-iotests/089.out |  8 ++++++++
 2 files changed, 28 insertions(+)

(limited to 'tests/qemu-iotests')

diff --git a/tests/qemu-iotests/089 b/tests/qemu-iotests/089
index 0b059aba90..aa1ba4a98e 100755
--- a/tests/qemu-iotests/089
+++ b/tests/qemu-iotests/089
@@ -82,6 +82,26 @@ $QEMU_IO_PROG --cache $CACHEMODE \
 $QEMU_IO -c 'read -P 42 0 512' "$TEST_IMG" | _filter_qemu_io
 
 
+echo
+echo "=== Testing correct handling of 'backing':null ==="
+echo
+
+_make_test_img -b "$TEST_IMG.base" $IMG_SIZE
+
+# This should read 42
+$QEMU_IO -c 'read -P 42 0 512' "$TEST_IMG" | _filter_qemu_io
+
+# This should read 0
+$QEMU_IO -c 'read -P 0 0 512' "json:{\
+    'driver': '$IMGFMT',
+    'file': {
+        'driver': 'file',
+        'filename': '$TEST_IMG'
+    },
+    'backing': null
+}" | _filter_qemu_io
+
+
 # Taken from test 071
 echo
 echo "=== Testing blkdebug ==="
diff --git a/tests/qemu-iotests/089.out b/tests/qemu-iotests/089.out
index 0bf5a13ec1..89e3e4340a 100644
--- a/tests/qemu-iotests/089.out
+++ b/tests/qemu-iotests/089.out
@@ -19,6 +19,14 @@ Pattern verification failed at offset 0, 512 bytes
 read 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
+=== Testing correct handling of 'backing':null ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+read 512/512 bytes at offset 0
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 512/512 bytes at offset 0
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
 === Testing blkdebug ===
 
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
-- 
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