block: Fix snapshot=on for protocol parsed from filename

Since commit 9fd3171a, BDRV_O_SNAPSHOT uses an option QDict to specify
the originally requested image as the backing file of the newly created
temporary snapshot. This means that the filename is stored in
"file.filename", which is an option that is not parsed for protocol
names. Therefore things like -drive file=nbd:localhost:10809 were
broken because it looked for a local file with the literal name
'nbd:localhost:10809'.

This patch changes the way BDRV_O_SNAPSHOT works once again. We now open
the originally requested image as normal, and then do a similar
operation as for live snapshots to put the temporary snapshot on top.
This way, both driver specific options and parsed filenames work.

As a nice side effect, this results in code movement to factor
bdrv_append_temp_snapshot() out. This is a good preparation for moving
its call to drive_init() and friends eventually.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/include/block/block.h b/include/block/block.h
index 1ed55d839a..b3230a25f6 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -190,6 +190,7 @@ int bdrv_open_image(BlockDriverState **pbs, const char *filename,
                     QDict *options, const char *bdref_key, int flags,
                     bool allow_none, Error **errp);
 int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp);
+void bdrv_append_temp_snapshot(BlockDriverState *bs, Error **errp);
 int bdrv_open(BlockDriverState **pbs, const char *filename,
               const char *reference, QDict *options, int flags,
               BlockDriver *drv, Error **errp);