[12/21] block: save the associated child name in BlockDriverState

diff --git a/block.c b/block.c
index 6d5c804..0558525 100644
--- a/block.c
+++ b/block.c
@@ -318,7 +318,8 @@  void bdrv_register(BlockDriver *bdrv)
 }
 
 /* create a new block device (by default it is empty) */
-BlockDriverState *bdrv_new(const char *device_name)
+static BlockDriverState *bdrv_new_int(const char *device_name,
+    BlockDriverState *child)
 {
     BlockDriverState *bs;
 
@@ -334,9 +335,24 @@  BlockDriverState *bdrv_new(const char *device_name)
     qemu_co_queue_init(&bs->throttled_reqs[1]);
     bs->refcnt = 1;
 
+    if (child) {
+        if (strlen(child->child_device_name)) {
+            pstrcpy(bs->child_device_name, sizeof(bs->child_device_name),
+                    child->child_device_name);
+        } else {
+            pstrcpy(bs->child_device_name, sizeof(bs->child_device_name),
+                    child->device_name);
+        }
+    }
+
     return bs;
 }
 
+BlockDriverState *bdrv_new(const char *device_name)
+{
+    return bdrv_new_int(device_name, NULL);
+}
+
 void bdrv_add_close_notifier(BlockDriverState *bs, Notifier *notify)
 {
     notifier_list_add(&bs->close_notifiers, notify);
@@ -847,16 +863,8 @@  free_and_fail:
     return ret;
 }
 
-/*
- * Opens a file using a protocol (file, host_device, nbd, ...)
- *
- * options is a QDict of options to pass to the block drivers, or NULL for an
- * empty set of options. The reference to the QDict belongs to the block layer
- * after the call (even on failure), so if the caller intends to reuse the
- * dictionary, it needs to use QINCREF() before calling bdrv_file_open.
- */
-int bdrv_file_open(BlockDriverState **pbs, const char *filename,
-                   QDict *options, int flags, Error **errp)
+static int bdrv_file_open_int(BlockDriverState **pbs, const char *filename,
+    QDict *options, int flags, BlockDriverState *child, Error **errp)
 {
     BlockDriverState *bs;
     BlockDriver *drv;
@@ -870,7 +878,7 @@  int bdrv_file_open(BlockDriverState **pbs, const char *filename,
         options = qdict_new();
     }
 
-    bs = bdrv_new("");
+    bs = bdrv_new_int("", child);
     bs->options = options;
     options = qdict_clone_shallow(options);
 
@@ -957,6 +965,20 @@  fail:
 }
 
 /*
+ * Opens a file using a protocol (file, host_device, nbd, ...)
+ *
+ * options is a QDict of options to pass to the block drivers, or NULL for an
+ * empty set of options. The reference to the QDict belongs to the block layer
+ * after the call (even on failure), so if the caller intends to reuse the
+ * dictionary, it needs to use QINCREF() before calling bdrv_file_open.
+ */
+int bdrv_file_open(BlockDriverState **pbs, const char *filename,
+                   QDict *options, int flags, Error **errp)
+{
+    return bdrv_file_open_int(pbs, filename, options, flags, NULL, errp);
+}
+
+/*
  * Opens the backing file for a BlockDriverState if not yet open
  *
  * options is a QDict of options to pass to the block drivers, or NULL for an
@@ -992,8 +1014,7 @@  int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
                                        sizeof(backing_filename));
     }
 
-    bs->backing_hd = bdrv_new("");
-
+    bs->backing_hd = bdrv_new_int("", bs);
     if (bs->backing_format[0] != '\0') {
         back_drv = bdrv_find_format(bs->backing_format);
     }
@@ -1063,7 +1084,7 @@  int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
            instead of opening 'filename' directly */
 
         /* if there is a backing file, use it */
-        bs1 = bdrv_new("");
+        bs1 = bdrv_new_int("", bs);
         ret = bdrv_open(bs1, filename, NULL, 0, drv, &local_err);
         if (ret < 0) {
             bdrv_unref(bs1);
@@ -1124,8 +1145,9 @@  int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
 
     qdict_extract_subqdict(options, &file_options, "file.");
 
-    ret = bdrv_file_open(&file, filename, file_options,
-                         bdrv_open_flags(bs, flags | BDRV_O_UNMAP), &local_err);
+    ret = bdrv_file_open_int(&file, filename, file_options,
+                             bdrv_open_flags(bs, flags | BDRV_O_UNMAP),
+                             bs, &local_err);
     if (ret < 0) {
         goto fail;
     }
@@ -1883,7 +1905,7 @@  int bdrv_commit(BlockDriverState *bs)
 
     if (!drv)
         return -ENOMEDIUM;
-    
+
     if (!bs->backing_hd) {
         return -ENOTSUP;
     }
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 1666066..e0f31dc 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -301,6 +301,7 @@  struct BlockDriverState {
     bool iostatus_enabled;
     BlockDeviceIoStatus iostatus;
     char device_name[32];
+    char child_device_name[32];
     HBitmap *dirty_bitmap;
     int refcnt;
     int in_use; /* users other than guest access, eg. block migration */