@@ -2597,7 +2597,9 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
/* See cautionary note on accessing @options above */
backing = qdict_get_try_str(options, "backing");
- if (backing && *backing == '\0') {
+ if (qobject_to(qdict_get(options, "backing"), QNull) != NULL ||
+ (backing && *backing == '\0'))
+ {
flags |= BDRV_O_NO_BACKING;
qdict_del(options, "backing");
}
@@ -3969,7 +3969,6 @@ void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
QObject *obj;
Visitor *v = qobject_output_visitor_new(&obj);
QDict *qdict;
- const QDictEntry *ent;
Error *local_err = NULL;
visit_type_BlockdevOptions(v, NULL, &options, &local_err);
@@ -3983,19 +3982,6 @@ void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
qdict_flatten(qdict);
- /*
- * Rewrite "backing": null to "backing": ""
- * TODO Rewrite "" to null instead, and perhaps not even here
- */
- for (ent = qdict_first(qdict); ent; ent = qdict_next(qdict, ent)) {
- char *dot = strrchr(ent->key, '.');
-
- if (!strcmp(dot ? dot + 1 : ent->key, "backing")
- && qobject_type(ent->value) == QTYPE_QNULL) {
- qdict_put(qdict, ent->key, qstring_new());
- }
- }
-
if (!qdict_get_try_str(qdict, "node-name")) {
error_setg(errp, "'node-name' must be specified for the root node");
goto fail;
@@ -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 ==="
@@ -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
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> --- block.c | 4 +++- blockdev.c | 14 -------------- tests/qemu-iotests/089 | 20 ++++++++++++++++++++ tests/qemu-iotests/089.out | 8 ++++++++ 4 files changed, 31 insertions(+), 15 deletions(-)