block: Factor out should_update_child()

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

1 files changed, 27 insertions, 15 deletions

diff --git a/block.c b/block.c
index f293ccb5af..6dc02b85aa 100644
--- a/block.c
+++ b/block.c
@@ -2886,28 +2886,40 @@ void bdrv_close_all(void)
     assert(QTAILQ_EMPTY(&all_bdrv_states));
 }
 
+static bool should_update_child(BdrvChild *c, BlockDriverState *to)
+{
+    BdrvChild *to_c;
+
+    if (c->role->stay_at_node) {
+        return false;
+    }
+
+    if (c->role == &child_backing) {
+        /* If @from is a backing file of @to, ignore the child to avoid
+         * creating a loop. We only want to change the pointer of other
+         * parents. */
+        QLIST_FOREACH(to_c, &to->children, next) {
+            if (to_c == c) {
+                break;
+            }
+        }
+        if (to_c) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
 static void change_parent_backing_link(BlockDriverState *from,
                                        BlockDriverState *to)
 {
-    BdrvChild *c, *next, *to_c;
+    BdrvChild *c, *next;
 
     QLIST_FOREACH_SAFE(c, &from->parents, next_parent, next) {
-        if (c->role->stay_at_node) {
+        if (!should_update_child(c, to)) {
             continue;
         }
-        if (c->role == &child_backing) {
-            /* If @from is a backing file of @to, ignore the child to avoid
-             * creating a loop. We only want to change the pointer of other
-             * parents. */
-            QLIST_FOREACH(to_c, &to->children, next) {
-                if (to_c == c) {
-                    break;
-                }
-            }
-            if (to_c) {
-                continue;
-            }
-        }
 
         bdrv_ref(to);
         /* FIXME Are we sure that bdrv_replace_child() can't run into