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-rw-r--r--block.c24
1 files changed, 15 insertions, 9 deletions
diff --git a/block.c b/block.c
index 8104225cd3..b331eb9d38 100644
--- a/block.c
+++ b/block.c
@@ -2226,9 +2226,23 @@ void bdrv_close_all(void)
static void change_parent_backing_link(BlockDriverState *from,
BlockDriverState *to)
{
- BdrvChild *c, *next;
+ BdrvChild *c, *next, *to_c;
QLIST_FOREACH_SAFE(c, &from->parents, next_parent, next) {
+ if (c->role == &child_backing) {
+ /* @from is generally not allowed to be a backing file, except for
+ * when @to is the overlay. In that case, @from may not be replaced
+ * by @to as @to's backing node. */
+ QLIST_FOREACH(to_c, &to->children, next) {
+ if (to_c == c) {
+ break;
+ }
+ }
+ if (to_c) {
+ continue;
+ }
+ }
+
assert(c->role != &child_backing);
bdrv_ref(to);
bdrv_replace_child(c, to);
@@ -2277,14 +2291,6 @@ void bdrv_replace_in_backing_chain(BlockDriverState *old, BlockDriverState *new)
change_parent_backing_link(old, new);
- /* Change backing files if a previously independent node is added to the
- * chain. For active commit, we replace top by its own (indirect) backing
- * file and don't do anything here so we don't build a loop. */
- if (new->backing == NULL && !bdrv_chain_contains(backing_bs(old), new)) {
- bdrv_set_backing_hd(new, backing_bs(old));
- bdrv_set_backing_hd(old, NULL);
- }
-
bdrv_unref(old);
}