This will be used in the following commit to bring "incremental" mode
to copy-before-write filter.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/block/block-copy.h |  2 +-
 block/block-copy.c         | 14 ++++++++++++--
 block/copy-before-write.c  |  2 +-
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/block/block-copy.h b/include/block/block-copy.h
index 99370fa38b..8da4cec1b6 100644
--- a/include/block/block-copy.h
+++ b/include/block/block-copy.h
@@ -25,7 +25,7 @@ typedef struct BlockCopyState BlockCopyState;
 typedef struct BlockCopyCallState BlockCopyCallState;
 
 BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
-                                     Error **errp);
+                                     BdrvDirtyBitmap *bitmap, Error **errp);
 
 /* Function should be called prior any actual copy request */
 void block_copy_set_copy_opts(BlockCopyState *s, bool use_copy_range,
diff --git a/block/block-copy.c b/block/block-copy.c
index c39cb5fda7..65019d0d1d 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -383,8 +383,9 @@ static int64_t block_copy_calculate_cluster_size(BlockDriverState *target,
 }
 
 BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
-                                     Error **errp)
+                                     BdrvDirtyBitmap *bitmap, Error **errp)
 {
+    ERRP_GUARD();
     BlockCopyState *s;
     int64_t cluster_size;
     BdrvDirtyBitmap *copy_bitmap;
@@ -401,7 +402,16 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
         return NULL;
     }
     bdrv_disable_dirty_bitmap(copy_bitmap);
-    bdrv_set_dirty_bitmap(copy_bitmap, 0, bdrv_dirty_bitmap_size(copy_bitmap));
+    if (bitmap) {
+        if (!bdrv_merge_dirty_bitmap(copy_bitmap, bitmap, NULL, errp)) {
+            error_prepend(errp, "Failed to merge bitmap '%s' to internal "
+                          "copy-bitmap: ", bdrv_dirty_bitmap_name(bitmap));
+            return NULL;
+        }
+    } else {
+        bdrv_set_dirty_bitmap(copy_bitmap, 0,
+                              bdrv_dirty_bitmap_size(copy_bitmap));
+    }
 
     /*
      * If source is in backing chain of target assume that target is going to be
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index f5551cd15b..d31ca61111 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -169,7 +169,7 @@ static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
             ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
              bs->file->bs->supported_zero_flags);
 
-    s->bcs = block_copy_state_new(bs->file, s->target, errp);
+    s->bcs = block_copy_state_new(bs->file, s->target, NULL, errp);
     if (!s->bcs) {
         error_prepend(errp, "Cannot create block-copy-state: ");
         return -EINVAL;
-- 
2.29.2