block: Allow recursive "file"s

It should be possible to use a format as a driver for a file which in
turn requires another file, i.e., nesting file formats.

Allowing nested file formats results in e.g. qcow2 BlockDriverStates
never being directly passed to bdrv_open_common() from bdrv_file_open(),
but instead being handed through bdrv_open(). This changes the error
message when trying to give a filename to qcow2, i.e. trying to use it
as a driver for the protocol level. Therefore, change the reference
output of I/O test 051 accordingly.

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

1 files changed, 7 insertions, 2 deletions

diff --git a/block.c b/block.c
index 9e4e85f..6af5f6e 100644
--- a/block.c
+++ b/block.c
@@ -948,14 +948,19 @@ int bdrv_file_open(BlockDriverState **pbs, const char *filename,
         goto fail;
     }
 
-    ret = bdrv_open_common(bs, NULL, options, flags, drv, &local_err);
+    if (!drv->bdrv_file_open) {
+        ret = bdrv_open(bs, filename, options, flags, drv, &local_err);
+        options = NULL;
+    } else {
+        ret = bdrv_open_common(bs, NULL, options, flags, drv, &local_err);
+    }
     if (ret < 0) {
         error_propagate(errp, local_err);
         goto fail;
     }
 
     /* Check if any unknown options were used */
-    if (qdict_size(options) != 0) {
+    if (options && (qdict_size(options) != 0)) {
         const QDictEntry *entry = qdict_first(options);
         error_setg(errp, "Block protocol '%s' doesn't support the option '%s'",
                    drv->format_name, entry->key);