diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index a4fee64..d7f1833 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -144,38 +144,37 @@
     }
 }
 
-static int cbw_init(BlockDriverState *top, BlockDriverState *source,
+static int cbw_init(BlockDriverState *bs, BlockDriverState *source,
                     BlockDriverState *target, bool compress, Error **errp)
 {
-    BDRVCopyBeforeWriteState *state = top->opaque;
+    BDRVCopyBeforeWriteState *s = bs->opaque;
 
-    top->total_sectors = source->total_sectors;
-    top->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
+    bs->total_sectors = source->total_sectors;
+    bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
             (BDRV_REQ_FUA & source->supported_write_flags);
-    top->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
+    bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
             ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
              source->supported_zero_flags);
 
     bdrv_ref(target);
-    state->target = bdrv_attach_child(top, target, "target", &child_of_bds,
-                                      BDRV_CHILD_DATA, errp);
-    if (!state->target) {
+    s->target = bdrv_attach_child(bs, target, "target", &child_of_bds,
+                                  BDRV_CHILD_DATA, errp);
+    if (!s->target) {
         error_prepend(errp, "Cannot attach target child: ");
         return -EINVAL;
     }
 
     bdrv_ref(source);
-    top->file = bdrv_attach_child(top, source, "file", &child_of_bds,
-                                  BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
-                                  errp);
-    if (!top->file) {
+    bs->file = bdrv_attach_child(bs, source, "file", &child_of_bds,
+                                 BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
+                                 errp);
+    if (!bs->file) {
         error_prepend(errp, "Cannot attach file child: ");
         return -EINVAL;
     }
 
-    state->bcs = block_copy_state_new(top->file, state->target, false, compress,
-                                      errp);
-    if (!state->bcs) {
+    s->bcs = block_copy_state_new(bs->file, s->target, false, compress, errp);
+    if (!s->bcs) {
         error_prepend(errp, "Cannot create block-copy-state: ");
         return -EINVAL;
     }