block: Make bdrv_child_get_parent_aio_context I/O

We want to use bdrv_child_get_parent_aio_context() from
bdrv_parent_drained_{begin,end}_single(), both of which are "I/O or GS"
functions.

Prior to 3ed4f708fe1, all the implementations were I/O code anyway.
3ed4f708fe1 has put block jobs' AioContext field under the job mutex, so
to make child_job_get_parent_aio_context() work in an I/O context, we
need to take that lock there.

Furthermore, blk_root_get_parent_aio_context() is not marked as
anything, but is safe to run in an I/O context, so mark it that way now.
(blk_get_aio_context() is an I/O code function.)

With that done, all implementations explicitly are I/O code, so we can
mark bdrv_child_get_parent_aio_context() as I/O code, too, so callers
know it is safe to run from both GS and I/O contexts.

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20221107151321.211175-2-hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index c0c7d56c8d..ed2f4b67a2 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -311,6 +311,7 @@ static void blk_root_detach(BdrvChild *child)
 static AioContext *blk_root_get_parent_aio_context(BdrvChild *c)
 {
     BlockBackend *blk = c->opaque;
+    IO_CODE();
 
     return blk_get_aio_context(blk);
 }