linux-kernel - Re: [PATCH] rust: lib: Add necessary unsafes for container

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Message-ID: <CANiq72kKnYHHi9R62HZcXGhOsWxPEmiVOXTJ9QS=NQMBSQ6KBQ@mail.gmail.com>
Date: Mon, 17 Nov 2025 09:59:27 +0100
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: phasta@...nel.org
Cc: Alice Ryhl <aliceryhl@...gle.com>, Miguel Ojeda <ojeda@...nel.org>, 
	Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Viresh Kumar <viresh.kumar@...aro.org>, 
	Tamir Duberstein <tamird@...il.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: lib: Add necessary unsafes for container_of

On Mon, Nov 17, 2025 at 9:24 AM Philipp Stanner <phasta@...lbox.org> wrote:
>
> OK, so container_of is an unsafe function and all uses of it must be
> guarded by an unsafe block.
>
> If I do this, however
>
> @@ -217,7 +217,7 @@ unsafe fn view_value(me: *mut $crate::list::ListLinks<$num>) -> *const Self {
> @@ -242,7 +242,7 @@ unsafe fn post_remove(me: *mut $crate::list::ListLinks<$num>) -> *const Self {
>
> then the compiler gets sad again, complaining precisely about the
> internals of container_of:
>
> 269 |               unsafe fn prepare_to_insert(me: *const Self) -> *mut $crate::list::ListLinks<$num> {
> 321 |               unsafe fn view_value(links_field: *mut $crate::list::ListLinks<$num>) -> *const Self {

Given the signatures above, it seems to me you have done it for 2 out
of 4 of the calls, thus the compiler complains as expected.

Cheers,
Miguel