[PATCH V9 04/17] iothread: introduce iothread_unsafe_get_aio_context()

[Zhang Chen <zhangckid@gmail.com>]

The iothread_unsafe_get_aio_context() is a low-level unsafe way of getting
the AioContext, recommend migrating to the new API with IOThreadHolder
as much as possible.

The blockdev is the first user:
Every BlockDriverState would need to get/put the IOThread AioContext in
bdrv_change_aio_context() or related functions.
However, the QEMU block layer has been moving away from having a
per-BlockDriverState AioContext. It is possible to use a
BlockDriverState from any AioContext (including multiple AioContexts at
the same time). I'm in favor of not associating BlockDriverStates with
IOThreads and instead relying on their device owners (e.g. emulated
storage controllers) to be the IOThread holders.

Signed-off-by: Zhang Chen <zhangckid@gmail.com>
---
 blockdev.c                | 2 +-
 include/system/iothread.h | 6 ++++++
 iothread.c                | 6 ++++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 6e86c6262f..baeab3a3e1 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3683,7 +3683,7 @@ void qmp_x_blockdev_set_iothread(const char *node_name, StrOrNull *iothread,
             goto out;
         }
 
-        new_context = iothread_get_aio_context(obj);
+        new_context = iothread_unsafe_get_aio_context(obj);
     } else {
         new_context = qemu_get_aio_context();
     }
diff --git a/include/system/iothread.h b/include/system/iothread.h
index b483bbfab3..064c05e78d 100644
--- a/include/system/iothread.h
+++ b/include/system/iothread.h
@@ -71,6 +71,12 @@ DECLARE_INSTANCE_CHECKER(IOThread, IOTHREAD,
 char *iothread_get_id(IOThread *iothread);
 IOThread *iothread_by_id(const char *id);
 AioContext *iothread_get_aio_context(IOThread *iothread);
+/*
+ * The iothread_unsafe_get_aio_context() is a low-level unsafe way of getting
+ * the AioContext, recommend migrating to the new API with IOThreadHolder
+ * as much as possible.
+ */
+AioContext *iothread_unsafe_get_aio_context(IOThread *iothread);
 AioContext *iothread_ref_and_get_aio_context(IOThread *iothread,
                                              const IOThreadHolder *holder);
 void iothread_put_aio_context(IOThread *iothread, const IOThreadHolder *holder);
diff --git a/iothread.c b/iothread.c
index 528002c34a..a85e960e45 100644
--- a/iothread.c
+++ b/iothread.c
@@ -468,6 +468,12 @@ void iothread_put_aio_context(IOThread *iothread, const IOThreadHolder *holder)
     iothread_unref(iothread, holder);
 }
 
+/* Recommend migrating to the new API with IOThreadHolder as much as possible */
+AioContext *iothread_unsafe_get_aio_context(IOThread *iothread)
+{
+    return iothread->ctx;
+}
+
 static int query_one_iothread(Object *object, void *opaque)
 {
     IOThreadInfoList ***tail = opaque;
-- 
2.49.0