@@ -83,6 +83,9 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
BdrvChildRole child_role,
Error **errp);
+static void bdrv_replace_child_noperm(BdrvChild *child,
+ BlockDriverState *new_bs);
+
static int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue
*queue, Error **errp);
static void bdrv_reopen_commit(BDRVReopenState *reopen_state);
@@ -2237,6 +2240,57 @@ static int bdrv_drv_set_perm(BlockDriverState *bs, uint64_t perm,
return 0;
}
+typedef struct BdrvReplaceChildState {
+ BdrvChild *child;
+ BlockDriverState *old_bs;
+} BdrvReplaceChildState;
+
+static void bdrv_replace_child_commit(void *opaque)
+{
+ BdrvReplaceChildState *s = opaque;
+
+ bdrv_unref(s->old_bs);
+}
+
+static void bdrv_replace_child_abort(void *opaque)
+{
+ BdrvReplaceChildState *s = opaque;
+ BlockDriverState *new_bs = s->child->bs;
+
+ /* old_bs reference is transparently moved from @s to @s->child */
+ bdrv_replace_child_noperm(s->child, s->old_bs);
+ bdrv_unref(new_bs);
+}
+
+static TransactionActionDrv bdrv_replace_child_drv = {
+ .commit = bdrv_replace_child_commit,
+ .abort = bdrv_replace_child_abort,
+ .clean = g_free,
+};
+
+/*
+ * bdrv_replace_child_safe
+ *
+ * Note: real unref of old_bs is done only on commit.
+ */
+__attribute__((unused))
+static void bdrv_replace_child_safe(BdrvChild *child, BlockDriverState *new_bs,
+ Transaction *tran)
+{
+ BdrvReplaceChildState *s = g_new(BdrvReplaceChildState, 1);
+ *s = (BdrvReplaceChildState) {
+ .child = child,
+ .old_bs = child->bs,
+ };
+ tran_add(tran, &bdrv_replace_child_drv, s);
+
+ if (new_bs) {
+ bdrv_ref(new_bs);
+ }
+ bdrv_replace_child_noperm(child, new_bs);
+ /* old_bs reference is transparently moved from @child to @s */
+}
+
/*
* Check whether permissions on this node can be changed in a way that
* @cumulative_perms and @cumulative_shared_perms are the new cumulative