Re: [linux-next:master 13069/13300] error[E0425]: cannot find value `VM_MERGEABLE` in crate `bindings`

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 3 Oct 2025 00:39:16 +0200 Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote:

> On Fri, Oct 3, 2025 at 12:27 AM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > Sorry, this is rather annoying.  Rust is breaking the build for a very
> > simple patch.  Many developers aren't rust-enabled and probably aren't
> > even able to test a fix - my attempt to get a rust build setup working
> > didn't end happily.
> >
> > Jakub's patch fixes a kernel crash and needs to be merged into mainline
> > and -stable reasonably soon.  But that is now blocked until someone who
> > knows how to fix this error and how to test it gets down and does those
> > things.
> >
> > Jakub's patch is present in current linux-next.  Can someone please
> > send us a fix?
> 
> I am not sure I follow -- the diff I gave you should work.

It would be nice if someone were to test it!

> If you have a branch you want me to test and/or give you a formal
> patch on top of that or similar, I can do that.

Thanks.  As mentioned, today's linux-next is where the problem is being
observed.

I'm queueing the below as a fixup against Jakub's original.  This should
appear in tomorrow's linux-next.  Or the day after - it's a timezone
thing.

From: Andrew Morton <akpm@linux-foundation.org>
Subject: mm-ksm-fix-flag-dropping-behavior-in-ksm_madvise-fix
Date: Thu Oct  2 03:37:47 PM PDT 2025

Rust bindgen wasn't able to handle the BIT() macro.  Add a helper (from
Miguel) to fix this.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202510030449.VfSaAjvd-lkp@intel.com/
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jakub Acs <acsjakub@amazon.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Xu Xin <xu.xin16@zte.com.cn>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 rust/bindings/bindings_helper.h |    1 +
 1 file changed, 1 insertion(+)

--- a/rust/bindings/bindings_helper.h~mm-ksm-fix-flag-dropping-behavior-in-ksm_madvise-fix
+++ a/rust/bindings/bindings_helper.h
@@ -99,3 +99,4 @@ const xa_mark_t RUST_CONST_HELPER_XA_PRE
 
 const gfp_t RUST_CONST_HELPER_XA_FLAGS_ALLOC = XA_FLAGS_ALLOC;
 const gfp_t RUST_CONST_HELPER_XA_FLAGS_ALLOC1 = XA_FLAGS_ALLOC1;
+const vm_flags_t RUST_CONST_HELPER_VM_MERGEABLE = VM_MERGEABLE;
_