also avoid populating the reverse cacher (pointing to DataFrame that …

…is parent of Series

pandas/core/generic.py

@@ -3752,6 +3752,11 @@ def _maybe_update_cacher(
         verify_is_copy : bool, default True
             Provide is_copy checks.
         """
+        if (
+            config.get_option("mode.copy_on_write")
+            and config.get_option("mode.data_manager") == "block"
+        ):
+            return
 
         if verify_is_copy:
             self._check_setitem_copy(t="referent")

pandas/core/series.py

@@ -1237,6 +1237,11 @@ def _set_as_cached(self, item, cacher) -> None:
         Set the _cacher attribute on the calling object with a weakref to
         cacher.
         """
+        if (
+            get_option("mode.copy_on_write")
+            and get_option("mode.data_manager") == "block"
+        ):
+            return
         self._cacher = (item, weakref.ref(cacher))
 
     def _clear_item_cache(self) -> None:
@@ -1260,6 +1265,13 @@ def _maybe_update_cacher(
         """
         See NDFrame._maybe_update_cacher.__doc__
         """
+        # for CoW, we never want to update the parent DataFrame cache
+        # if the Series changed, but don't keep track of any cacher
+        if (
+            get_option("mode.copy_on_write")
+            and get_option("mode.data_manager") == "block"
+        ):
+            return
         cacher = getattr(self, "_cacher", None)
         if cacher is not None:
             assert self.ndim == 1
@@ -1269,16 +1281,7 @@ def _maybe_update_cacher(
             # a copy
             if ref is None:
                 del self._cacher
-            # for CoW, we never want to update the parent DataFrame cache
-            # if the Series changed, and always pop the cached item
-            elif (
-                not (
-                    get_option("mode.copy_on_write")
-                    and get_option("mode.data_manager") == "block"
-                )
-                and len(self) == len(ref)
-                and self.name in ref.columns
-            ):
+            elif len(self) == len(ref) and self.name in ref.columns:
                 # GH#42530 self.name must be in ref.columns
                 # to ensure column still in dataframe
                 # otherwise, either self or ref has swapped in new arrays