diff options
Diffstat (limited to 'block.c')
| -rw-r--r-- | block.c | 43 |
1 files changed, 37 insertions, 6 deletions
@@ -3542,7 +3542,9 @@ void bdrv_close_all(void) static bool should_update_child(BdrvChild *c, BlockDriverState *to) { - BdrvChild *to_c; + GQueue *queue; + GHashTable *found; + bool ret; if (c->role->stay_at_node) { return false; @@ -3578,14 +3580,43 @@ static bool should_update_child(BdrvChild *c, BlockDriverState *to) * if A is a child of B, that means we cannot replace A by B there * because that would create a loop. Silently detaching A from B * is also not really an option. So overall just leaving A in - * place there is the most sensible choice. */ - QLIST_FOREACH(to_c, &to->children, next) { - if (to_c == c) { - return false; + * place there is the most sensible choice. + * + * We would also create a loop in any cases where @c is only + * indirectly referenced by @to. Prevent this by returning false + * if @c is found (by breadth-first search) anywhere in the whole + * subtree of @to. + */ + + ret = true; + found = g_hash_table_new(NULL, NULL); + g_hash_table_add(found, to); + queue = g_queue_new(); + g_queue_push_tail(queue, to); + + while (!g_queue_is_empty(queue)) { + BlockDriverState *v = g_queue_pop_head(queue); + BdrvChild *c2; + + QLIST_FOREACH(c2, &v->children, next) { + if (c2 == c) { + ret = false; + break; + } + + if (g_hash_table_contains(found, c2->bs)) { + continue; + } + + g_queue_push_tail(queue, c2->bs); + g_hash_table_add(found, c2->bs); } } - return true; + g_queue_free(queue); + g_hash_table_destroy(found); + + return ret; } void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to, |