block: Add bdrv_aio_cancel_async

This is the async version of bdrv_aio_cancel, which doesn't block the
caller. It guarantees that the cb is called either before returning or
some time later.

bdrv_aio_cancel can base on bdrv_aio_cancel_async, later we can convert
all .io_cancel implementations to .io_cancel_async, and the aio_poll is
the common logic. In the end, .io_cancel can be dropped.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/block/aio.h b/include/block/aio.h
index 2626fc745f..ad361e34c7 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -27,6 +27,8 @@ typedef void BlockDriverCompletionFunc(void *opaque, int ret);
 
 typedef struct AIOCBInfo {
     void (*cancel)(BlockDriverAIOCB *acb);
+    void (*cancel_async)(BlockDriverAIOCB *acb);
+    AioContext *(*get_aio_context)(BlockDriverAIOCB *acb);
     size_t aiocb_size;
 } AIOCBInfo;