diff --git a/block.c b/block.c
index 1205ef8..d287771 100644
--- a/block.c
+++ b/block.c
@@ -3195,9 +3195,9 @@
 {
     BlockDriverState *bs;
     Error *local_err = NULL;
-    BdrvNextIterator *it = NULL;
+    BdrvNextIterator it;
 
-    while ((it = bdrv_next(it, &bs)) != NULL) {
+    for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *aio_context = bdrv_get_aio_context(bs);
 
         aio_context_acquire(aio_context);
@@ -3239,11 +3239,11 @@
 int bdrv_inactivate_all(void)
 {
     BlockDriverState *bs = NULL;
-    BdrvNextIterator *it = NULL;
+    BdrvNextIterator it;
     int ret = 0;
     int pass;
 
-    while ((it = bdrv_next(it, &bs)) != NULL) {
+    for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         aio_context_acquire(bdrv_get_aio_context(bs));
     }
 
@@ -3252,8 +3252,7 @@
      * the second pass sets the BDRV_O_INACTIVE flag so that no further write
      * is allowed. */
     for (pass = 0; pass < 2; pass++) {
-        it = NULL;
-        while ((it = bdrv_next(it, &bs)) != NULL) {
+        for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
             ret = bdrv_inactivate_recurse(bs, pass);
             if (ret < 0) {
                 goto out;
@@ -3262,8 +3261,7 @@
     }
 
 out:
-    it = NULL;
-    while ((it = bdrv_next(it, &bs)) != NULL) {
+    for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         aio_context_release(bdrv_get_aio_context(bs));
     }
 
@@ -3753,10 +3751,10 @@
 bool bdrv_is_first_non_filter(BlockDriverState *candidate)
 {
     BlockDriverState *bs;
-    BdrvNextIterator *it = NULL;
+    BdrvNextIterator it;
 
     /* walk down the bs forest recursively */
-    while ((it = bdrv_next(it, &bs)) != NULL) {
+    for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         bool perm;
 
         /* try to recurse in this top level bs */