[Qemu-block] [PATCH 2/8] block: Drop useless bdrv_new() calls

[Max Reitz]

bdrv_append_temp_snapshot() uses bdrv_new() to create an empty BDS
before invoking bdrv_open() on that BDS. This is probably a relict from
when it used to do some modifications on that empty BDS, but now that is
unnecessary, so we can just set bs_snapshot to NULL and let bdrv_open()
do the rest.

The same applies to bdrv_open_backing_file(). There is even a bit more
cruft here: The assert() was intended for the BDS which is indirectly
passed as the first bdrv_open() argument, so we can now drop it, too.

Signed-off-by: Max Reitz <address@hidden>
---
 block.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/block.c b/block.c
index 5b02990..aae1d69 100644
--- a/block.c
+++ b/block.c
@@ -1212,19 +1212,15 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict 
*options, Error **errp)
         goto free_exit;
     }
 
-    backing_hd = bdrv_new();
-
     if (bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) {
         qdict_put(options, "driver", qstring_from_str(bs->backing_format));
     }
 
-    assert(bs->backing == NULL);
+    backing_hd = NULL;
     ret = bdrv_open_inherit(&backing_hd,
                             *backing_filename ? backing_filename : NULL,
                             NULL, options, 0, bs, &child_backing, &local_err);
     if (ret < 0) {
-        bdrv_unref(backing_hd);
-        backing_hd = NULL;
         bs->open_flags |= BDRV_O_NO_BACKING;
         error_setg(errp, "Could not open backing file: %s",
                    error_get_pretty(local_err));
@@ -1350,8 +1346,7 @@ int bdrv_append_temp_snapshot(BlockDriverState *bs, int 
flags, Error **errp)
     qdict_put(snapshot_options, "driver",
               qstring_from_str("qcow2"));
 
-    bs_snapshot = bdrv_new();
-
+    bs_snapshot = NULL;
     ret = bdrv_open(&bs_snapshot, NULL, NULL, snapshot_options,
                     flags, &local_err);
     if (ret < 0) {
-- 
2.6.2