block: Adjust AioContexts when attaching nodes

So far, we only made sure that updating the AioContext of a node
affected the whole subtree. However, if a node is newly attached to a
new parent, we also need to make sure that both the subtree of the node
and the parent are in the same AioContext. This tries to move the new
child node to the parent AioContext and returns an error if this isn't
possible.

BlockBackends now actually apply their AioContext to their root node.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/blockjob.c b/blockjob.c
index 29517ae162..931d675c0c 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -205,8 +205,14 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs,
     BdrvChild *c;
 
     bdrv_ref(bs);
-    c = bdrv_root_attach_child(bs, name, &child_job, perm, shared_perm,
-                               job, errp);
+    if (job->job.aio_context != qemu_get_aio_context()) {
+        aio_context_release(job->job.aio_context);
+    }
+    c = bdrv_root_attach_child(bs, name, &child_job, job->job.aio_context,
+                               perm, shared_perm, job, errp);
+    if (job->job.aio_context != qemu_get_aio_context()) {
+        aio_context_acquire(job->job.aio_context);
+    }
     if (c == NULL) {
         return -EPERM;
     }