block: Really pause block jobs on drain

We already requested that block jobs be paused in .bdrv_drained_begin,
but no guarantee was made that the job was actually inactive at the
point where bdrv_drained_begin() returned.

This introduces a new callback BdrvChildRole.bdrv_drained_poll() and
uses it to make bdrv_drain_poll() consider block jobs using the node to
be drained.

For the test case to work as expected, we have to switch from
block_job_sleep_ns() to qemu_co_sleep_ns() so that the test job is even
considered active and must be waited for when draining the node.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/include/block/blockjob_int.h b/include/block/blockjob_int.h
index 5cd50c6639..e4a318dd15 100644
--- a/include/block/blockjob_int.h
+++ b/include/block/blockjob_int.h
@@ -39,6 +39,14 @@ struct BlockJobDriver {
     JobDriver job_driver;
 
     /*
+     * Returns whether the job has pending requests for the child or will
+     * submit new requests before the next pause point. This callback is polled
+     * in the context of draining a job node after requesting that the job be
+     * paused, until all activity on the child has stopped.
+     */
+    bool (*drained_poll)(BlockJob *job);
+
+    /*
      * If the callback is not NULL, it will be invoked before the job is
      * resumed in a new AioContext.  This is the place to move any resources
      * besides job->blk to the new AioContext.