Re: [RFC PATCH 1/5] rust: block: introduce `kernel::block::mq` module

From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
To: Andreas Hindborg <nmi@metaspace.dk>
Cc: "Boqun Feng" <boqun.feng@gmail.com>,
	"Jens Axboe" <axboe@kernel.dk>, "Christoph Hellwig" <hch@lst.de>,
	"Keith Busch" <kbusch@kernel.org>,
	"Damien Le Moal" <Damien.LeMoal@wdc.com>,
	"Bart Van Assche" <bvanassche@acm.org>,
	"Hannes Reinecke" <hare@suse.de>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"Andreas Hindborg" <a.hindborg@samsung.com>,
	"Wedson Almeida Filho" <wedsonaf@gmail.com>,
	"Niklas Cassel" <Niklas.Cassel@wdc.com>,
	"Greg KH" <gregkh@linuxfoundation.org>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Chaitanya Kulkarni" <chaitanyak@nvidia.com>,
	"Luis Chamberlain" <mcgrof@kernel.org>,
	"Yexuan Yang" <1182282462@bupt.edu.cn>,
	"Sergio González Collado" <sergio.collado@gmail.com>,
	"Joel Granados" <j.granados@samsung.com>,
	"Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>,
	"Daniel Gomez" <da.gomez@samsung.com>,
	"open list" <linux-kernel@vger.kernel.org>,
	"rust-for-linux@vger.kernel.org" <rust-for-linux@vger.kernel.org>,
	"lsf-pc@lists.linux-foundation.org"
	<lsf-pc@lists.linux-foundation.org>,
	"gost.dev@samsung.com" <gost.dev@samsung.com>
Subject: Re: [RFC PATCH 1/5] rust: block: introduce `kernel::block::mq` module
Date: Thu, 14 Mar 2024 21:56:31 +0100	[thread overview]
Message-ID: <CANiq72noqwU9_wC28Emc2LNyD70JFcS+4MXWuwYUTUWq8ragCg@mail.gmail.com> (raw)
In-Reply-To: <CANiq72neNUL1m0AbY78eXWJMov4fgjnNcQ_16SoT=ikJ3K7bZQ@mail.gmail.com>

On Thu, Mar 14, 2024 at 8:41 PM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> In any case, if we really want to avoid exporting the original symbol
> (perhaps so that "only Rust" can use it -- or someone trying hard to
> bypass things on purpose), then we could still avoid the helper and
> instead write a non-generic `kernel`-private Rust function instead.

The advantages would be that we get the export done automatically and
that we could write in Rust, e.g. with restricted visibility.

But we could need `#[inline(never)]` (or ideally `#[used]` if it could
go on functions) or `#[no_mangle]` (but we would lose the mangling).

Anyway, the simplest is to export the original symbol, but we could
consider to provide support one way or another for this kind of
"helpers" (i.e. leaving the current helpers as those for macros and
inline functions), so that it is clear what symbols are only exported
for Rust use (and not other C code).

Cheers,
Miguel