block: move drain outside of quorum_del_child()

The quorum_del_child() callback runs under the graph lock, so it is
not allowed to drain. It is only called as the .bdrv_del_child()
callback, which is only called in the bdrv_del_child() function, which
also runs under the graph lock.

The bdrv_del_child() function is called by qmp_x_blockdev_change().
A drained section was already introduced there by commit "block: move
drain out of quorum_add_child()".

This finally finishes moving out the drain to places that are not
under the graph lock started in "block: move draining out of
bdrv_change_aio_context() and mark GRAPH_RDLOCK".

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-17-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/block.c b/block.c
index 15a8ccb822..bfd4340b24 100644
--- a/block.c
+++ b/block.c
@@ -8276,6 +8276,8 @@ void bdrv_add_child(BlockDriverState *parent_bs, BlockDriverState *child_bs,
 /*
  * Hot remove a BDS's child. Used in combination with bdrv_add_child, so the
  * user can take a child offline when it is broken and take a new child online.
+ *
+ * All block nodes must be drained.
  */
 void bdrv_del_child(BlockDriverState *parent_bs, BdrvChild *child, Error **errp)
 {