linux-kernel - Re: [PATCH 3/5] mm: export zap_page_range_single and list_lru

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Message-ID: <CANiq72=ybFtqsh18zkC3e1iyR-RoffcL_ZDr-fU7SjzJiFERHw@mail.gmail.com>
Date: Thu, 5 Feb 2026 13:24:09 +0100
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: "David Hildenbrand (arm)" <david@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Carlos Llamas <cmllamas@...gle.com>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>, 
	"Serge E. Hallyn" <serge@...lyn.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Dave Chinner <david@...morbit.com>, Qi Zheng <zhengqi.arch@...edance.com>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>, 
	Miguel Ojeda <ojeda@...nel.org>, 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>, kernel-team@...roid.com, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-security-module@...r.kernel.org, linux-mm@...ck.org, 
	rust-for-linux@...r.kernel.org, Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 3/5] mm: export zap_page_range_single and list_lru_add/del

On Thu, Feb 5, 2026 at 12:58 PM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> wrote:
>
> What??
>
> Alice - can you confirm rust isn't exporting stuff that isn't explicitly marked
> EXPORT_SYMBOL*() for use by other rust modules?
>
> It's important we keep this in sync, otherwise rust is overriding kernel policy.

Currently, Rust GPL-exports every mangled symbol from the `kernel`
crate. To call something you would need to be a Rust caller (not C --
that is not supported at all, even if technically you could hack
something up) and the Rust API would then need to give you access to
it (i.e. you need to be able to pass the Rust language rules, e.g.
being public etc.).

In this case if we are talking about the `VmaRef` type, someone that
can get a reference to a value of that type could then call the
`zap_page_range_single` method. That in turns would try to call the C
one, but that one is not exported, right? So it should be fine.

In the future, for Rust, we may specify whether a particular crate
exports or not (and perhaps even allow to export non-GPL, but
originally it was decided to only export GPL stuff to be on the safe
side; and perhaps in certain namespaces etc.).

Cheers,
Miguel