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

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Message-ID: <cb09ffd3-0db8-4db4-923a-f707b4537441@meta.com>
Date: Tue, 13 Jan 2026 14:14:26 -0500
From: Chris Mason <clm@...a.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
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Subject: Re: [PATCH v3 1/4] mm: declare VMA flags by bit

On 1/13/26 2:09 PM, Lorenzo Stoakes wrote:
> On Tue, Jan 13, 2026 at 10:51:37AM -0800, Chris Mason wrote:
>> 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;
>>
>> [ ... ]
>>
>>
> 
> Oopsies!
> 
> I can send a patch unless you were planning to!

Please do, I'm still going through the rest of the commits.

-chris