Commit e59a0cf1 authored by Max Reitz's avatar Max Reitz Committed by Eric Blake
Browse files

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: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarAlberto Garcia <berto@igalia.com>
Message-Id: <20180224154033.29559-7-mreitz@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
[eblake: rebase to qobject_to() parameter order and qapi headers split]
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
parent 532fb532

block.c

+4 −1
Original line number Diff line number Diff line
@@ -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");

    }

blockdev.c

+0 −14
Original line number Diff line number Diff line
@@ -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;

tests/qemu-iotests/089

+20 −0
Original line number Diff line number Diff line
@@ -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 ==="

tests/qemu-iotests/089.out

+8 −0
Original line number Diff line number Diff line
@@ -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