block: Add bdrv_new_open_driver()

This function allows to create more or less normal BlockDriverStates
even for BlockDrivers that aren't globally registered (e.g. helper
filters for block jobs).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

2 files changed, 31 insertions, 1 deletions

diff --git a/block.c b/block.c
index f96d26b795..1368cf5409 100644
--- a/block.c
+++ b/block.c
@@ -939,13 +939,16 @@ static int bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv,
     }
 
     bs->drv = drv;
+    bs->read_only = !(bs->open_flags & BDRV_O_RDWR);
     bs->opaque = g_malloc0(drv->instance_size);
 
     if (drv->bdrv_file_open) {
         assert(!drv->bdrv_needs_filename || bs->filename[0]);
         ret = drv->bdrv_file_open(bs, options, open_flags, &local_err);
-    } else {
+    } else if (drv->bdrv_open) {
         ret = drv->bdrv_open(bs, options, open_flags, &local_err);
+    } else {
+        ret = 0;
     }
 
     if (ret < 0) {
@@ -986,6 +989,31 @@ free_and_fail:
     return ret;
 }
 
+BlockDriverState *bdrv_new_open_driver(BlockDriver *drv, const char *node_name,
+                                       int flags, Error **errp)
+{
+    BlockDriverState *bs;
+    int ret;
+
+    bs = bdrv_new();
+    bs->open_flags = flags;
+    bs->explicit_options = qdict_new();
+    bs->options = qdict_new();
+    bs->opaque = NULL;
+
+    update_options_from_flags(bs->options, flags);
+
+    ret = bdrv_open_driver(bs, drv, node_name, bs->options, flags, errp);
+    if (ret < 0) {
+        QDECREF(bs->explicit_options);
+        QDECREF(bs->options);
+        bdrv_unref(bs);
+        return NULL;
+    }
+
+    return bs;
+}
+
 QemuOptsList bdrv_runtime_opts = {
     .name = "bdrv_common",
     .head = QTAILQ_HEAD_INITIALIZER(bdrv_runtime_opts.head),
diff --git a/include/block/block.h b/include/block/block.h
index a4cd06f884..bde5ebda18 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -215,6 +215,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
                            const char *bdref_key, Error **errp);
 BlockDriverState *bdrv_open(const char *filename, const char *reference,
                             QDict *options, int flags, Error **errp);
+BlockDriverState *bdrv_new_open_driver(BlockDriver *drv, const char *node_name,
+                                       int flags, Error **errp);
 BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
                                     BlockDriverState *bs,
                                     QDict *options, int flags);