Finally, copy-before-write gets own .bdrv_open and .bdrv_close
handlers, block_init() call and becomes available through bdrv_open().

To achieve this:

 - cbw_init gets unused flags argument and becomes cbw_open
 - block_copy_state_free() call moved to new cbw_close()
 - in bdrv_cbw_append:
   - options are completed with driver and node-name, and we can simply
     use bdrv_insert_node() to do both open and drained replacing
 - in bdrv_cbw_drop:
   - cbw_close() is now responsible for freeing s->bcs, so don't do it
     here

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
 block/copy-before-write.c | 60 ++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 32 deletions(-)

diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index 2efe098aae..2cd68b480a 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -144,7 +144,8 @@ static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
     }
 }
 
-static int cbw_init(BlockDriverState *bs, QDict *options, Error **errp)
+static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
+                    Error **errp)
 {
     BDRVCopyBeforeWriteState *s = bs->opaque;
     BdrvDirtyBitmap *copy_bitmap;
@@ -181,10 +182,21 @@ static int cbw_init(BlockDriverState *bs, QDict *options, Error **errp)
     return 0;
 }
 
+static void cbw_close(BlockDriverState *bs)
+{
+    BDRVCopyBeforeWriteState *s = bs->opaque;
+
+    block_copy_state_free(s->bcs);
+    s->bcs = NULL;
+}
+
 BlockDriver bdrv_cbw_filter = {
     .format_name = "copy-before-write",
     .instance_size = sizeof(BDRVCopyBeforeWriteState),
 
+    .bdrv_open                  = cbw_open,
+    .bdrv_close                 = cbw_close,
+
     .bdrv_co_preadv             = cbw_co_preadv,
     .bdrv_co_pwritev            = cbw_co_pwritev,
     .bdrv_co_pwrite_zeroes      = cbw_co_pwrite_zeroes,
@@ -205,56 +217,40 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
                                   Error **errp)
 {
     ERRP_GUARD();
-    int ret;
     BDRVCopyBeforeWriteState *state;
     BlockDriverState *top;
     QDict *opts;
 
     assert(source->total_sectors == target->total_sectors);
 
-    top = bdrv_new_open_driver(&bdrv_cbw_filter, filter_node_name,
-                               BDRV_O_RDWR, errp);
-    if (!top) {
-        error_prepend(errp, "Cannot open driver: ");
-        return NULL;
-    }
-    state = top->opaque;
-
     opts = qdict_new();
+    qdict_put_str(opts, "driver", "copy-before-write");
+    if (filter_node_name) {
+        qdict_put_str(opts, "node-name", filter_node_name);
+    }
     qdict_put_str(opts, "file", bdrv_get_node_name(source));
     qdict_put_str(opts, "target", bdrv_get_node_name(target));
 
-    ret = cbw_init(top, opts, errp);
-    qobject_unref(opts);
-    if (ret < 0) {
-        goto fail;
-    }
-
-    bdrv_drained_begin(source);
-    ret = bdrv_replace_node(source, top, errp);
-    bdrv_drained_end(source);
-    if (ret < 0) {
-        error_prepend(errp, "Cannot append copy-before-write filter: ");
-        goto fail;
+    top = bdrv_insert_node(source, opts, BDRV_O_RDWR, errp);
+    if (!top) {
+        return NULL;
     }
 
+    state = top->opaque;
     *bcs = state->bcs;
 
     return top;
-
-fail:
-    block_copy_state_free(state->bcs);
-    bdrv_unref(top);
-    return NULL;
 }
 
 void bdrv_cbw_drop(BlockDriverState *bs)
 {
-    BDRVCopyBeforeWriteState *s = bs->opaque;
-
     bdrv_drop_filter(bs, &error_abort);
-
-    block_copy_state_free(s->bcs);
-
     bdrv_unref(bs);
 }
+
+static void cbw_init(void)
+{
+    bdrv_register(&bdrv_cbw_filter);
+}
+
+block_init(cbw_init);
-- 
2.29.2