block: JSON filenames and relative backing files
When using a relative backing file name, qemu needs to know the directory of the top image file. For JSON filenames, such a directory cannot be easily determined (e.g. how do you determine the directory of a qcow2 BDS directly on top of a quorum BDS?). Therefore, do not allow relative filenames for the backing file of BDSs only having a JSON filename. Furthermore, BDS::exact_filename should be used whenever possible. If BDS::filename is not equal to BDS::exact_filename, the former will always be a JSON object. Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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			@ -305,19 +305,28 @@ void path_combine(char *dest, int dest_size,
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void bdrv_get_full_backing_filename_from_filename(const char *backed,
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                                                  const char *backing,
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                                                  char *dest, size_t sz)
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                                                  char *dest, size_t sz,
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                                                  Error **errp)
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{
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    if (backing[0] == '\0' || path_has_protocol(backing)) {
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    if (backing[0] == '\0' || path_has_protocol(backing) ||
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        path_is_absolute(backing))
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    {
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        pstrcpy(dest, sz, backing);
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    } else if (backed[0] == '\0' || strstart(backed, "json:", NULL)) {
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        error_setg(errp, "Cannot use relative backing file names for '%s'",
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                   backed);
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    } else {
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        path_combine(dest, sz, backed, backing);
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    }
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}
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void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t sz)
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void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t sz,
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                                    Error **errp)
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{
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    bdrv_get_full_backing_filename_from_filename(bs->filename, bs->backing_file,
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                                                 dest, sz);
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    char *backed = bs->exact_filename[0] ? bs->exact_filename : bs->filename;
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    bdrv_get_full_backing_filename_from_filename(backed, bs->backing_file,
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                                                 dest, sz, errp);
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}
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void bdrv_register(BlockDriver *bdrv)
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			@ -1225,7 +1234,14 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
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        QDECREF(options);
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        goto free_exit;
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    } else {
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        bdrv_get_full_backing_filename(bs, backing_filename, PATH_MAX);
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        bdrv_get_full_backing_filename(bs, backing_filename, PATH_MAX,
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                                       &local_err);
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        if (local_err) {
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            ret = -EINVAL;
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            error_propagate(errp, local_err);
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            QDECREF(options);
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            goto free_exit;
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        }
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    }
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    if (!bs->drv || !bs->drv->supports_backing) {
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			@ -214,7 +214,12 @@ void bdrv_query_image_info(BlockDriverState *bs,
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        info->backing_filename = g_strdup(backing_filename);
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        info->has_backing_filename = true;
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        bdrv_get_full_backing_filename(bs, backing_filename2,
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                                       sizeof(backing_filename2));
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                                       sizeof(backing_filename2), &err);
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        if (err) {
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            error_propagate(errp, err);
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            qapi_free_ImageInfo(info);
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            return;
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        }
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        if (strcmp(backing_filename, backing_filename2) != 0) {
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            info->full_backing_filename =
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			@ -396,10 +396,11 @@ const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
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void bdrv_get_backing_filename(BlockDriverState *bs,
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                               char *filename, int filename_size);
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void bdrv_get_full_backing_filename(BlockDriverState *bs,
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                                    char *dest, size_t sz);
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                                    char *dest, size_t sz, Error **errp);
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void bdrv_get_full_backing_filename_from_filename(const char *backed,
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                                                  const char *backing,
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                                                  char *dest, size_t sz);
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                                                  char *dest, size_t sz,
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                                                  Error **errp);
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int bdrv_is_snapshot(BlockDriverState *bs);
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int path_has_protocol(const char *path);
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