linux-kernel - Re: [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags

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Message-Id: <9ff58468-a72d-4984-95f4-d0a60554705d@app.fastmail.com>
Date: Tue, 20 Jan 2026 17:44:29 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Lorenzo Stoakes" <lorenzo.stoakes@...cle.com>
Cc: "Jason Gunthorpe" <jgg@...dia.com>,
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Subject: Re: [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags_t only

On Tue, Jan 20, 2026, at 17:22, Lorenzo Stoakes wrote:
> On Tue, Jan 20, 2026 at 05:00:28PM +0100, Arnd Bergmann wrote:
>> On Tue, Jan 20, 2026, at 16:10, Lorenzo Stoakes wrote:
>> >
>> > It strikes me that the key optimisation here is the inlining, now if the issue
>> > is that ye olde compiler might choose not to inline very small functions (seems
>> > unlikely) we could always throw in an __always_inline?
>>
>> I can think of three specific things going wrong with structures passed
>> by value:
>
> I mean now you seem to be talking about it _in general_ which, _in theory_,
> kills the whole concept of bitmap VMA flags _altogether_ really, or at
> least any workable version of them.

No, what I'm saying is "understand what the pitfalls are", not
"don't do it". I think that is what Jason was also getting at.

     Arnd