block: wrlock in bdrv_replace_child_noperm

Protect the main function where graph is modified.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20221207131838.239125-12-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/block.c b/block.c
index 44d59362d6..df52c6b012 100644
--- a/block.c
+++ b/block.c
@@ -2836,8 +2836,6 @@ uint64_t bdrv_qapi_perm_to_blk_perm(BlockPermission qapi_perm)
  *
  * If @new_bs is non-NULL, the parent of @child must already be drained through
  * @child.
- *
- * This function does not poll.
  */
 static void bdrv_replace_child_noperm(BdrvChild *child,
                                       BlockDriverState *new_bs)
@@ -2875,23 +2873,24 @@ static void bdrv_replace_child_noperm(BdrvChild *child,
         assert(bdrv_get_aio_context(old_bs) == bdrv_get_aio_context(new_bs));
     }
 
+    /* TODO Pull this up into the callers to avoid polling here */
+    bdrv_graph_wrlock();
     if (old_bs) {
         if (child->klass->detach) {
             child->klass->detach(child);
         }
-        assert_bdrv_graph_writable(old_bs);
         QLIST_REMOVE(child, next_parent);
     }
 
     child->bs = new_bs;
 
     if (new_bs) {
-        assert_bdrv_graph_writable(new_bs);
         QLIST_INSERT_HEAD(&new_bs->parents, child, next_parent);
         if (child->klass->attach) {
             child->klass->attach(child);
         }
     }
+    bdrv_graph_wrunlock();
 
     /*
      * If the parent was drained through this BdrvChild previously, but new_bs