change_parent_backing_link() asserts that the BDS to be replaced is not
used as a backing file. However, we may want to replace a BDS by its
overlay in which case that very link should not be redirected.
Signed-off-by: Max Reitz <mre...@redhat.com>
---
block.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/block.c b/block.c
index f54bc25..16463aa 100644
--- a/block.c
+++ b/block.c
@@ -2224,9 +2224,22 @@ 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) {
+ /* Allow @from to be in a backing chain, but only if it is @to's
+ * backing chain. Do not replace @from by @to there. */
+ 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);
--
2.8.3
