Re: [PATCH 5/7] rust: file: add `Kuid` wrapper

From: Christian Brauner <brauner@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Alice Ryhl" <aliceryhl@google.com>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Wedson Almeida Filho" <wedsonaf@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"Andreas Hindborg" <a.hindborg@samsung.com>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Arve Hjønnevåg" <arve@android.com>,
	"Todd Kjos" <tkjos@android.com>,
	"Martijn Coenen" <maco@android.com>,
	"Joel Fernandes" <joel@joelfernandes.org>,
	"Carlos Llamas" <cmllamas@google.com>,
	"Suren Baghdasaryan" <surenb@google.com>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Daniel Xu" <dxu@dxuuu.xyz>,
	linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 5/7] rust: file: add `Kuid` wrapper
Date: Thu, 30 Nov 2023 13:46:36 +0100	[thread overview]
Message-ID: <20231130-wohle-einfuhr-1708e9c3e596@brauner> (raw)
In-Reply-To: <20231129164815.GI23596@noisy.programming.kicks-ass.net>

On Wed, Nov 29, 2023 at 05:48:15PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 29, 2023 at 05:28:27PM +0100, Christian Brauner wrote:
> 
> > > +pid_t rust_helper_task_tgid_nr_ns(struct task_struct *tsk,
> > > +				  struct pid_namespace *ns)
> > > +{
> > > +	return task_tgid_nr_ns(tsk, ns);
> > > +}
> > > +EXPORT_SYMBOL_GPL(rust_helper_task_tgid_nr_ns);
> > 
> > I'm a bit puzzled by all these rust_helper_*() calls. Can you explain
> > why they are needed? Because they are/can be static inlines and that
> > somehow doesn't work?
> 
> Correct, because Rust can only talk to C ABI, it cannot use C headers.
> Bindgen would need to translate the full C headers into valid Rust for
> that to work.
> 
> I really think the Rust peoples should spend more effort on that,
> because you are quite right, all this wrappery is tedious at best.

The problem is that we end up with a long list of explicit exports that
also are all really weirdly named like rust_helper_*(). I wouldn't even
complain if it they were somehow auto-generated but as you say that
might be out of scope.

The thing is though that if I want to change the static inlines I know
also have to very likely care about these explicit Rust wrappers which
seems less than ideal.

So if we could not do rust_helper_*() exports we'd probably be better
off.