block: Make bdrv_parent_drained_begin/end public

Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>

block/io.c

@@ -44,7 +44,7 @@ static void coroutine_fn bdrv_co_do_rw(void *opaque);
 static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
     int64_t offset, int count, BdrvRequestFlags flags);
 
-static void bdrv_parent_drained_begin(BlockDriverState *bs)
+void bdrv_parent_drained_begin(BlockDriverState *bs)
 {
     BdrvChild *c;
 
@@ -55,7 +55,7 @@ static void bdrv_parent_drained_begin(BlockDriverState *bs)
     }
 }
 
-static void bdrv_parent_drained_end(BlockDriverState *bs)
+void bdrv_parent_drained_end(BlockDriverState *bs)
 {
     BdrvChild *c;
 

include/block/block.h

@@ -572,6 +572,22 @@ int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo);
 void bdrv_io_plug(BlockDriverState *bs);
 void bdrv_io_unplug(BlockDriverState *bs);
 
+/**
+ * bdrv_parent_drained_begin:
+ *
+ * Begin a quiesced section of all users of @bs. This is part of
+ * bdrv_drained_begin.
+ */
+void bdrv_parent_drained_begin(BlockDriverState *bs);
+
+/**
+ * bdrv_parent_drained_end:
+ *
+ * End a quiesced section of all users of @bs. This is part of
+ * bdrv_drained_end.
+ */
+void bdrv_parent_drained_end(BlockDriverState *bs);
+
 /**
  * bdrv_drained_begin:
  *