diff --git a/block.c b/block.c
index 7547051ec2abd8cf84e495d097a83358bc9cc49e..c07ff390ce16f0903cecb17c341d61cdde2a1e17 100644
--- a/block.c
+++ b/block.c
@@ -2569,6 +2569,55 @@ int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
     return data.ret;
 }
 
+/*
+ * Given an image chain: ... -> [BASE] -> [INTER1] -> [INTER2] -> [TOP]
+ *
+ * Return true if the given sector is allocated in any image between
+ * BASE and TOP (inclusive).  BASE can be NULL to check if the given
+ * sector is allocated in any image of the chain.  Return false otherwise.
+ *
+ * 'pnum' is set to the number of sectors (including and immediately following
+ *  the specified sector) that are known to be in the same
+ *  allocated/unallocated state.
+ *
+ */
+int coroutine_fn bdrv_co_is_allocated_above(BlockDriverState *top,
+                                            BlockDriverState *base,
+                                            int64_t sector_num,
+                                            int nb_sectors, int *pnum)
+{
+    BlockDriverState *intermediate;
+    int ret, n = nb_sectors;
+
+    intermediate = top;
+    while (intermediate && intermediate != base) {
+        int pnum_inter;
+        ret = bdrv_co_is_allocated(intermediate, sector_num, nb_sectors,
+                                   &pnum_inter);
+        if (ret < 0) {
+            return ret;
+        } else if (ret) {
+            *pnum = pnum_inter;
+            return 1;
+        }
+
+        /*
+         * [sector_num, nb_sectors] is unallocated on top but intermediate
+         * might have
+         *
+         * [sector_num+x, nr_sectors] allocated.
+         */
+        if (n > pnum_inter) {
+            n = pnum_inter;
+        }
+
+        intermediate = intermediate->backing_hd;
+    }
+
+    *pnum = n;
+    return 0;
+}
+
 BlockInfoList *qmp_query_block(Error **errp)
 {
     BlockInfoList *head = NULL, *cur_item = NULL;
diff --git a/block.h b/block.h
index 7408acc5cd305adf421b7727bd5485364ae29257..799cf48cc2f72a8eefffa097d8766748707e89f6 100644
--- a/block.h
+++ b/block.h
@@ -165,6 +165,10 @@ int coroutine_fn bdrv_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
     int nb_sectors);
 int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs, int64_t sector_num,
     int nb_sectors, int *pnum);
+int coroutine_fn bdrv_co_is_allocated_above(BlockDriverState *top,
+                                            BlockDriverState *base,
+                                            int64_t sector_num,
+                                            int nb_sectors, int *pnum);
 BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
     const char *backing_file);
 int bdrv_truncate(BlockDriverState *bs, int64_t offset);
diff --git a/block/stream.c b/block/stream.c
index 4490a25ba2787efe42ab4c35eb6841c86f2e676c..811388a4026dd86f3f4f9d3a83bff95ecd2d328f 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -98,55 +98,6 @@ static void close_unused_images(BlockDriverState *top, BlockDriverState *base,
     top->backing_hd = base;
 }
 
-/*
- * Given an image chain: [BASE] -> [INTER1] -> [INTER2] -> [TOP]
- *
- * Return true if the given sector is allocated in any image between
- * BASE and TOP (inclusive).  BASE can be NULL to check if the given
- * sector is allocated in any image of the chain.  Return false otherwise.
- *
- * 'pnum' is set to the number of sectors (including and immediately following
- *  the specified sector) that are known to be in the same
- *  allocated/unallocated state.
- *
- */
-static int coroutine_fn is_allocated_above(BlockDriverState *top,
-                                           BlockDriverState *base,
-                                           int64_t sector_num,
-                                           int nb_sectors, int *pnum)
-{
-    BlockDriverState *intermediate;
-    int ret, n = nb_sectors;
-
-    intermediate = top;
-    while (intermediate != base) {
-        int pnum_inter;
-        ret = bdrv_co_is_allocated(intermediate, sector_num, nb_sectors,
-                                   &pnum_inter);
-        if (ret < 0) {
-            return ret;
-        } else if (ret) {
-            *pnum = pnum_inter;
-            return 1;
-        }
-
-        /*
-         * [sector_num, nb_sectors] is unallocated on top but intermediate
-         * might have
-         *
-         * [sector_num+x, nr_sectors] allocated.
-         */
-        if (n > pnum_inter) {
-            n = pnum_inter;
-        }
-
-        intermediate = intermediate->backing_hd;
-    }
-
-    *pnum = n;
-    return 0;
-}
-
 static void coroutine_fn stream_run(void *opaque)
 {
     StreamBlockJob *s = opaque;
@@ -196,10 +147,10 @@ wait:
         } else {
             /* Copy if allocated in the intermediate images.  Limit to the
              * known-unallocated area [sector_num, sector_num+n).  */
-            ret = is_allocated_above(bs->backing_hd, base, sector_num, n, &n);
+            ret = bdrv_co_is_allocated_above(bs->backing_hd, base,
+                                             sector_num, n, &n);
             copy = (ret == 1);
         }
-
         trace_stream_one_iteration(s, sector_num, n, ret);
         if (ret >= 0 && copy) {
             if (s->common.speed) {