Fix TODO in make_tensor_for_subclass_helper (pytorch#162336)

The constructor does accept a DataPtr (had to fix the DataPtr variant not accepting a SymInt, though).
Pull Request resolved: pytorch#162336
Approved by: https://github.com/ezyang
ghstack dependencies: pytorch#162298

Author: swolchok

c10/core/Storage.h

@@ -61,6 +61,22 @@ struct C10_API Storage {
             allocator,
             resizable)) {}
 
+  // Creates storage with pre-allocated memory buffer. Allocator is given for
+  // potential future reallocations, however it can be nullptr if the storage
+  // is non-resizable
+  Storage(
+      use_byte_size_t /*use_byte_size*/,
+      SymInt size_bytes,
+      at::DataPtr data_ptr,
+      at::Allocator* allocator = nullptr,
+      bool resizable = false)
+      : storage_impl_(c10::make_intrusive<StorageImpl>(
+            StorageImpl::use_byte_size_t(),
+            std::move(size_bytes),
+            std::move(data_ptr),
+            allocator,
+            resizable)) {}
+
  protected:
   explicit Storage(unsafe_borrow_t, const Storage& rhs)
       : storage_impl_(c10::intrusive_ptr<c10::StorageImpl>::reclaim(

torch/csrc/autograd/python_variable.cpp

@@ -660,10 +660,9 @@ static Tensor make_tensor_for_subclass_helper(
   Storage storage{
       Storage::use_byte_size_t{},
       size_bytes,
+      at::DataPtr{nullptr, options.device()},
       /*allocator=*/c10::GetAllocator(c10::kMeta),
       /*resizable=*/true};
-  // TODO: constructor should probably accept data pointer
-  storage.set_data_ptr_noswap(at::DataPtr{nullptr, options.device()});
 
   auto keys = c10::DispatchKeySet({options.computeDispatchKey()});
   if (extra_dispatch_keys.has_value()) {