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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>
This commit is contained in:
Max Reitz 2018-02-24 16:40:32 +01:00 committed by Eric Blake
parent 532fb53284
commit e59a0cf17b
4 changed files with 32 additions and 15 deletions
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5
block.c
View File

@ -33,6 +33,7 @@
#include "qapi/error.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qjson.h"
#include "qapi/qmp/qnull.h"
#include "qapi/qmp/qstring.h"
#include "qapi/qobject-output-visitor.h"
#include "qapi/qapi-visit-block-core.h"
@ -2645,7 +2646,9 @@ 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(QNull, qdict_get(options, "backing")) != NULL ||
(backing && *backing == '\0'))
{
flags |= BDRV_O_NO_BACKING;
qdict_del(options, "backing");
}

14
blockdev.c
View File

@ -4045,7 +4045,6 @@ 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);
@ -4059,19 +4058,6 @@ 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;

20
tests/qemu-iotests/089
View File

@ -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 ==="

8
tests/qemu-iotests/089.out
View File

@ -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