2 files changed, 14 insertions, 0 deletions
diff --git a/block.c b/block.c
index d36eb75be9..d4939b49bf 100644
--- a/block.c
+++ b/block.c
@@ -1526,6 +1526,13 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
         if (!bs) {
             return -ENODEV;
         }
+
+        if (bs->throttle_state) {
+            error_setg(errp, "Cannot reference an existing block device for "
+                       "which I/O throttling is enabled");
+            return -EINVAL;
+        }
+
         bdrv_ref(bs);
         *pbs = bs;
         return 0;
diff --git a/blockdev.c b/blockdev.c
index 332068a837..f1f520a265 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2661,6 +2661,13 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
         goto out;
     }
 
+    /* The BlockBackend must be the only parent */
+    assert(QLIST_FIRST(&bs->parents));
+    if (QLIST_NEXT(QLIST_FIRST(&bs->parents), next_parent)) {
+        error_setg(errp, "Cannot throttle device with multiple parents");
+        goto out;
+    }
+
     throttle_config_init(&cfg);
     cfg.buckets[THROTTLE_BPS_TOTAL].avg = bps;
     cfg.buckets[THROTTLE_BPS_READ].avg  = bps_rd;