It's a BlockBackend wrapper of bdrv_co_copy_range.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block/block-backend.c          | 8 ++++++++
 include/sysemu/block-backend.h | 4 ++++
 2 files changed, 12 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 681b240b12..54b0789282 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2217,3 +2217,11 @@ void blk_unregister_buf(BlockBackend *blk, void *host)
 {
     bdrv_unregister_buf(blk_bs(blk), host);
 }
+
+int coroutine_fn blk_co_copy_range(BlockBackend *blk_in, int64_t off_in,
+                                   BlockBackend *blk_out, int64_t off_out,
+                                   int bytes)
+{
+    return bdrv_co_copy_range(blk_in->root, off_in, blk_out->root, off_out,
+                              bytes);
+}
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 92ab624fac..1fde14b461 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -232,4 +232,8 @@ void blk_set_force_allow_inactivate(BlockBackend *blk);
 void blk_register_buf(BlockBackend *blk, void *host, size_t size);
 void blk_unregister_buf(BlockBackend *blk, void *host);
 
+int blk_co_copy_range(BlockBackend *blk_in, int64_t off_in,
+                      BlockBackend *blk_out, int64_t off_out,
+                      int bytes);
+
 #endif
-- 
2.14.3