rust compile failure in next-20260730

[Bert Karwatzki <spasswolf@web.de>]

With next-20260730 building a kernel with CONFIG_RUST=y fails with
the following error:

 RUSTC L rust/kernel.o
error[E0308]: mismatched types
     --> rust/kernel/sync/poll.rs:175:44
      |
  175 |         unsafe { bindings::kvfree_call_rcu((*ptr).rcu.get(), ptr.cast::<ffi::c_void>()) };
      |                  ------------------------- ^^^^^^^^^^^^^^^^ expected `*mut kvfree_rcu_head`, found `*mut callback_head`
      |                  |
      |                  arguments to this function are incorrect
      |
      = note: expected raw pointer `*mut bindings::kvfree_rcu_head`
                 found raw pointer `*mut bindings::callback_head`
note: function defined here
     --> /mnt/data/linux-forest/linux-next/rust/bindings/bindings_generated.rs:73708:12
      |
73708 |     pub fn kvfree_call_rcu(head: *mut kvfree_rcu_head, ptr: *mut ffi::c_void);
      |            ^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.
make[5]: *** [rust/Makefile:781: rust/kernel.o] Fehler 1
make[4]: *** [Makefile:1420: prepare] Fehler 2
make[3]: *** [debian/rules:80: build-arch] Fehler 2

Reverting the following commits:
ef32a74f8f6a ("mm/slab: introduce kfree_rcu_nolock()")
bdd0cc9f0ffc ("mm/slab: introduce struct kvfree_rcu_head for kvfree_rcu batching")
    
make the compilation work again.   

Bert Karwatzki