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

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Message-ID: <aYSKD7RQQGuFFkqx@google.com>
Date: Thu, 5 Feb 2026 12:16:15 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: "David Hildenbrand (arm)" <david@...nel.org>, 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
Subject: Re: [PATCH 3/5] mm: export zap_page_range_single and list_lru_add/del

On Thu, Feb 05, 2026 at 12:10:38PM +0000, Lorenzo Stoakes wrote:
> On Thu, Feb 05, 2026 at 11:58:00AM +0000, Alice Ryhl wrote:
> > On Thu, Feb 05, 2026 at 12:43:03PM +0100, David Hildenbrand (arm) wrote:
> > > On 2/5/26 12:29, Lorenzo Stoakes wrote:
> > > > On Thu, Feb 05, 2026 at 10:51:28AM +0000, Alice Ryhl wrote:
> > > > >   bool list_lru_del_obj(struct list_lru *lru, struct list_head *item)
> > > > >   {
> > > > > diff --git a/mm/memory.c b/mm/memory.c
> > > > > index da360a6eb8a48e29293430d0c577fb4b6ec58099..64083ace239a2caf58e1645dd5d91a41d61492c4 100644
> > > > > --- a/mm/memory.c
> > > > > +++ b/mm/memory.c
> > > > > @@ -2168,6 +2168,7 @@ void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
> > > > >   	zap_page_range_single_batched(&tlb, vma, address, size, details);
> > > > >   	tlb_finish_mmu(&tlb);
> > > > >   }
> > > > > +EXPORT_SYMBOL(zap_page_range_single);
> > > >
> > > > Sorry but I don't want this exported at all.
> > > >
> > > > This is an internal implementation detail which allows fine-grained control of
> > > > behaviour via struct zap_details (which binder doesn't use, of course :)
> > >
> > > I don't expect anybody to set zap_details, but yeah, it could be abused.
> > > It could be abused right now from anywhere else in the kernel
> > > where we don't build as a module :)
> > >
> > > Apparently we export a similar function in rust where we just removed the last parameter.
> >
> > To clarify, said Rust function gets inlined into Rust Binder, so Rust
> > Binder calls the zap_page_range_single() symbol directly.
> 
> Presumably only for things compiled into the kernel right?

No, building Rust Binder with =m triggers this error for me:

ERROR: modpost: "zap_page_range_single" [drivers/android/binder/rust_binder.ko] undefined!

Alice