linux-kernel - Re: [PATCH v3 1/4] mm: declare VMA flags by bit

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Message-ID: <20260113185142.254821-1-clm@meta.com>
Date: Tue, 13 Jan 2026 10:51:37 -0800
From: Chris Mason <clm@...a.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
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Subject: Re: [PATCH v3 1/4] mm: declare VMA flags by bit

On Tue, 25 Nov 2025 10:00:59 +0000 Lorenzo Stoakes <lorenzo.stoakes@...cle.com> wrote:

[ ... ]
> 
> Finally, we update the rust binding helper as now it cannot auto-detect the
> flags at all.
> 

I did a run of all the MM commits from 6.18 to today's linus, and this one
had a copy/paste error.   I'd normally just send a patch for this, but in
terms of showing the review output:

> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 2e43c66635a2c..4c327db01ca03 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -108,7 +108,32 @@ const xa_mark_t RUST_CONST_HELPER_XA_PRESENT = XA_PRESENT;

[ ... ]

> +const vm_flags_t RUST_CONST_HELPER_VM_MAYREAD = VM_MAYREAD;
> +const vm_flags_t RUST_CONST_HELPER_VM_MAYWRITE = VM_MAYWRITE;
> +const vm_flags_t RUST_CONST_HELPER_VM_MAYEXEC = VM_MAYEXEC;
> +const vm_flags_t RUST_CONST_HELPER_VM_MAYSHARE = VM_MAYEXEC;
                                                   ^^^^^^^^^^

Should this be VM_MAYSHARE instead of VM_MAYEXEC? This appears to be a
copy-paste error that would cause Rust code using VmFlags::MAYSHARE to
get bit 6 (VM_MAYEXEC) instead of bit 7 (VM_MAYSHARE).

The pattern of the preceding lines shows each constant should reference
its matching flag:

    RUST_CONST_HELPER_VM_MAYREAD  = VM_MAYREAD
    RUST_CONST_HELPER_VM_MAYWRITE = VM_MAYWRITE
    RUST_CONST_HELPER_VM_MAYEXEC  = VM_MAYEXEC
    RUST_CONST_HELPER_VM_MAYSHARE = VM_MAYSHARE  <- expected

> +const vm_flags_t RUST_CONST_HELPER_VM_PFNMAP = VM_PFNMAP;

[ ... ]