linux-kernel - Re: [PATCH 0/4] initial work on making VMA flags a bitmap

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Message-ID: <aQNPXcxcxcX3Lwv0@google.com>
Date: Thu, 30 Oct 2025 11:43:25 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Nico Pache <npache@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Muchun Song <muchun.song@...ux.dev>, Oscar Salvador <osalvador@...e.de>, 
	David Hildenbrand <david@...hat.com>, "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>, Axel Rasmussen <axelrasmussen@...gle.com>, 
	Yuanchu Xie <yuanchu@...gle.com>, Wei Xu <weixugc@...gle.com>, Peter Xu <peterx@...hat.com>, 
	Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, 
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, Kees Cook <kees@...nel.org>, 
	Matthew Wilcox <willy@...radead.org>, Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>, 
	Leon Romanovsky <leon@...nel.org>, Zi Yan <ziy@...dia.com>, 
	Baolin Wang <baolin.wang@...ux.alibaba.com>, Ryan Roberts <ryan.roberts@....com>, 
	Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>, Lance Yang <lance.yang@...ux.dev>, 
	Xu Xin <xu.xin16@....com.cn>, Chengming Zhou <chengming.zhou@...ux.dev>, 
	Jann Horn <jannh@...gle.com>, Matthew Brost <matthew.brost@...el.com>, 
	Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>, 
	Byungchul Park <byungchul@...com>, Gregory Price <gourry@...rry.net>, 
	Ying Huang <ying.huang@...ux.alibaba.com>, Alistair Popple <apopple@...dia.com>, 
	Pedro Falcato <pfalcato@...e.de>, Shakeel Butt <shakeel.butt@...ux.dev>, 
	David Rientjes <rientjes@...gle.com>, Rik van Riel <riel@...riel.com>, Harry Yoo <harry.yoo@...cle.com>, 
	Kemeng Shi <shikemeng@...weicloud.com>, Kairui Song <kasong@...cent.com>, 
	Nhat Pham <nphamcs@...il.com>, Baoquan He <bhe@...hat.com>, Chris Li <chrisl@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>, Qi Zheng <zhengqi.arch@...edance.com>, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCH 0/4] initial work on making VMA flags a bitmap

On Thu, Oct 30, 2025 at 08:33:10AM +0000, Lorenzo Stoakes wrote:
> +cc Alice - could you help look at this? It seems I have broken the rust
> bindings here :)
> 
> Thanks!
> 
> On Wed, Oct 29, 2025 at 09:07:07PM -0600, Nico Pache wrote:
> > Hey Lorenzo,
> >
> > I put your patchset into the Fedora Koji system to run some CI on it for you.
> >
> > It failed to build due to what looks like some Rust bindings.
> >
> > Heres the build: https://koji.fedoraproject.org/koji/taskinfo?taskID=138547842
> >
> > And x86 build logs:
> > https://kojipkgs.fedoraproject.org//work/tasks/7966/138547966/build.log
> >
> > The error is pretty large but here's a snippet if you want an idea
> >
> > error[E0425]: cannot find value `VM_READ` in crate `bindings`
> >    --> rust/kernel/mm/virt.rs:399:44
> >     |
> > 399 |     pub const READ: vm_flags_t = bindings::VM_READ as vm_flags_t;
> >     |                                            ^^^^^^^ not found in `bindings`
> > error[E0425]: cannot find value `VM_WRITE` in crate `bindings`
> >    --> rust/kernel/mm/virt.rs:402:45
> >     |
> > 402 |     pub const WRITE: vm_flags_t = bindings::VM_WRITE as vm_flags_t;
> >     |                                             ^^^^^^^^ not found
> > in `bindings`
> > error[E0425]: cannot find value `VM_EXEC` in crate `bindings`
> >      --> rust/kernel/mm/virt.rs:405:44
> >       |
> >   405 |     pub const EXEC: vm_flags_t = bindings::VM_EXEC as vm_flags_t;
> >       |                                            ^^^^^^^ help: a
> > constant with a similar name exists: `ET_EXEC`
> >       |
> >      ::: /builddir/build/BUILD/kernel-6.18.0-build/kernel-6.18-rc3-16-ge53642b87a4f/linux-6.18.0-0.rc3.e53642b87a4f.31.bitvma.fc44.x86_64/rust/bindings/bindings_generated.rs:13881:1
> >       |
> > 13881 | pub const ET_EXEC: u32 = 2;
> >       | ---------------------- similarly named constant `ET_EXEC` defined here
> > error[E0425]: cannot find value `VM_SHARED` in crate `bindings`
> >    --> rust/kernel/mm/virt.rs:408:46
> >     |
> > 408 |     pub const SHARED: vm_flags_t = bindings::VM_SHARED as vm_flags_t;
> >     |                                              ^^^^^^^^^ not found
> > in `bindings`
> >
> > In the next version Ill do the same and continue with the CI testing for you!
> 
> Thanks much appreciated :)
> 
> It seems I broke the rust bindings (clearly), have pinged Alice to have a
> look!
> 
> May try and repro my side to see if there's something trivial that I could
> take a look at.
> 
> I ran this through mm self tests, allmodconfig + a bunch of other checks
> but ofc enabling rust was not one, I should probably update my scripts [0]
> to do that too :)
> 
> Cheers, Lorenzo
> 
> [0]:https://github.com/lorenzo-stoakes/review-scripts

I can help convert the Rust bindings to work with this approach. I see
there is a nice and simple vma_test() method for checking a flag, but I
don't see any equivalent method for setting or unsetting a given bit.
What would be the best function for Rust to call to set or unset a given
bit in the vma flags?

Alice