block: Make sure throttled BDSes always have a BB

It was already true in principle that a throttled BDS always has a BB
attached, except that the order of operations while attaching or
detaching a BDS to/from a BB wasn't careful enough.

This commit breaks graph manipulations while I/O throttling is enabled.
It would have been possible to keep things working with some temporary
hacks, but quite cumbersome, so it's not worth the hassle. We'll fix
things again in a minute.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/tests/test-throttle.c b/tests/test-throttle.c
index 744a524368..77b95d6380 100644
--- a/tests/test-throttle.c
+++ b/tests/test-throttle.c
@@ -574,11 +574,16 @@ static void test_accounting(void)
 static void test_groups(void)
 {
     ThrottleConfig cfg1, cfg2;
+    BlockBackend *blk1, *blk2, *blk3;
     BlockDriverState *bdrv1, *bdrv2, *bdrv3;
 
-    bdrv1 = bdrv_new();
-    bdrv2 = bdrv_new();
-    bdrv3 = bdrv_new();
+    blk1 = blk_new_with_bs(&error_abort);
+    blk2 = blk_new_with_bs(&error_abort);
+    blk3 = blk_new_with_bs(&error_abort);
+
+    bdrv1 = blk_bs(blk1);
+    bdrv2 = blk_bs(blk2);
+    bdrv3 = blk_bs(blk3);
 
     g_assert(bdrv1->throttle_state == NULL);
     g_assert(bdrv2->throttle_state == NULL);