If a protocol driver does not support image creation, we can see whether maybe the file exists already. If so, just truncating it will be sufficient.
Signed-off-by: Max Reitz <mre...@redhat.com> --- block.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 65 insertions(+), 12 deletions(-) diff --git a/block.c b/block.c index c139540f2b..8fb8e4dfda 100644 --- a/block.c +++ b/block.c @@ -531,20 +531,57 @@ out: return ret; } -int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp) +static int bdrv_create_file_fallback(const char *filename, BlockDriver *drv, + QemuOpts *opts, Error **errp) { - BlockDriver *drv; + BlockBackend *blk; + QDict *options = qdict_new(); + int64_t size = 0; + char *buf = NULL; + PreallocMode prealloc; Error *local_err = NULL; int ret; + size = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0); + buf = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC); + prealloc = qapi_enum_parse(&PreallocMode_lookup, buf, + PREALLOC_MODE_OFF, &local_err); + g_free(buf); + if (local_err) { + error_propagate(errp, local_err); + return -EINVAL; + } + + qdict_put_str(options, "driver", drv->format_name); + + blk = blk_new_open(filename, NULL, options, + BDRV_O_RDWR | BDRV_O_RESIZE, errp); + if (!blk) { + error_prepend(errp, "Protocol driver '%s' does not support " + "image creation, and opening the image failed: ", + drv->format_name); + return -EINVAL; + } + + ret = blk_truncate(blk, size, prealloc, errp); + blk_unref(blk); + return ret; +} + +int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp) +{ + BlockDriver *drv; + drv = bdrv_find_protocol(filename, true, errp); if (drv == NULL) { return -ENOENT; } - ret = bdrv_create(drv, filename, opts, &local_err); - error_propagate(errp, local_err); - return ret; + if (drv->bdrv_co_create_opts) { + return bdrv_create(drv, filename, opts, errp); + } else { + return bdrv_create_file_fallback(filename, drv, opts, errp); + } } /** @@ -1420,6 +1457,24 @@ QemuOptsList bdrv_runtime_opts = { }, }; +static QemuOptsList fallback_create_opts = { + .name = "fallback-create-opts", + .head = QTAILQ_HEAD_INITIALIZER(fallback_create_opts.head), + .desc = { + { + .name = BLOCK_OPT_SIZE, + .type = QEMU_OPT_SIZE, + .help = "Virtual disk size" + }, + { + .name = BLOCK_OPT_PREALLOC, + .type = QEMU_OPT_STRING, + .help = "Preallocation mode (allowed values: off)" + }, + { /* end of list */ } + } +}; + /* * Common part for opening disk images and files * @@ -5681,14 +5736,12 @@ void bdrv_img_create(const char *filename, const char *fmt, return; } - if (!proto_drv->create_opts) { - error_setg(errp, "Protocol driver '%s' does not support image creation", - proto_drv->format_name); - return; - } - create_opts = qemu_opts_append(create_opts, drv->create_opts); - create_opts = qemu_opts_append(create_opts, proto_drv->create_opts); + if (proto_drv->create_opts) { + create_opts = qemu_opts_append(create_opts, proto_drv->create_opts); + } else { + create_opts = qemu_opts_append(create_opts, &fallback_create_opts); + } /* Create parameter list with default values */ opts = qemu_opts_create(create_opts, NULL, 0, &error_abort); -- 2.21.0