Doing the opposite can make ->detach() (more precisely bdrv_unapply_subtree_drain() in bdrv_child_cb_detach) undo the subtree_drain just performed to protect the removal of the child from the graph, thus making the fully-enabled assert_bdrv_graph_writable fail.
Note that assert_bdrv_graph_writable is not yet fully enabled. Signed-off-by: Emanuele Giuseppe Esposito <[email protected]> --- block.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/block.c b/block.c index 372f16f4a0..d870ba5393 100644 --- a/block.c +++ b/block.c @@ -1448,6 +1448,11 @@ static void bdrv_child_cb_attach(BdrvChild *child) bdrv_apply_subtree_drain(child, bs); } +/* + * Unapply the drain in the whole child subtree, as + * it has been already detached, and then remove from + * child->opaque->children. + */ static void bdrv_child_cb_detach(BdrvChild *child) { BlockDriverState *bs = child->opaque; @@ -2864,14 +2869,18 @@ static void bdrv_replace_child_noperm(BdrvChild **childp, } if (old_bs) { - /* Detach first so that the recursive drain sections coming from @child - * are already gone and we only end the drain sections that came from - * elsewhere. */ + /* First remove child from child->bs->parents list */ + assert_bdrv_graph_writable(old_bs); + QLIST_REMOVE(child, next_parent); + /* + * Then call ->detach() cb. + * In child_of_bds case, update the child parent + * (child->opaque) ->children list and + * remove any drain left in the child subtree. + */ if (child->klass->detach) { child->klass->detach(child); } - assert_bdrv_graph_writable(old_bs); - QLIST_REMOVE(child, next_parent); } child->bs = new_bs; -- 2.31.1
