Max Reitz <mre...@redhat.com> writes: > 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 <mre...@redhat.com> > --- > block.c | 2 +- > blockdev.c | 14 -------------- > tests/qemu-iotests/089 | 20 ++++++++++++++++++++ > tests/qemu-iotests/089.out | 8 ++++++++ > 4 files changed, 29 insertions(+), 15 deletions(-) > > diff --git a/block.c b/block.c > index 85427df577..bc92ddd5a0 100644 > --- a/block.c > +++ b/block.c > @@ -2558,7 +2558,7 @@ 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 (qdict_is_qnull(options, "backing") || (backing && *backing == '\0')) > { > flags |= BDRV_O_NO_BACKING; > qdict_del(options, "backing"); > }
Consider a comment pointing out "" is deprecated. See also my reply to PATCH 1/3. > diff --git a/blockdev.c b/blockdev.c > index 56a6b24a0b..99ef618b39 100644 > --- a/blockdev.c > +++ b/blockdev.c > @@ -3885,7 +3885,6 @@ 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); > @@ -3899,19 +3898,6 @@ 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; > diff --git a/tests/qemu-iotests/089 b/tests/qemu-iotests/089 > index 9bfe2307b3..832eac1248 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 18f5fdda7a..607a9c6d9c 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 Reviewed-by: Markus Armbruster <arm...@redhat.com>