From: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "Jason Gunthorpe" <jgg@nvidia.com>,
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Subject: Re: [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags_t only
Date: Tue, 20 Jan 2026 16:50:21 +0000 [thread overview]
Message-ID: <7ac64213-26f9-470c-bf6a-abd1c0f6c83d@lucifer.local> (raw)
In-Reply-To: <9ff58468-a72d-4984-95f4-d0a60554705d@app.fastmail.com>
On Tue, Jan 20, 2026 at 05:44:29PM +0100, Arnd Bergmann wrote:
> 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
Ack sure and your input is appreciated :) It's important to kick the tyres
and be aware of possible issues.
Actually I think now I understand where Jason's coming from - the by-value
cases will be const value for the most part - which should make life MUCH
easier for the compiler and avoid a lot of the issues you raised.
So _hopefully_ we're mitigated. Again as I said, in cases where we might
not be, I will take action to figure out workarounds.
I'm excited by the proposed approach in general (+ again thanks to Jason to
opening my eyes to the possibility in the first place), so perhaps a
_little_ defensive, as it allows for a like-for-like replacement generally
which should HUGELY speed up + simplify the transition :)
Cheers, Lorenzo
next prev parent reply other threads:[~2026-01-20 16:50 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-19 21:19 [PATCH RESEND 00/12] mm: add bitmap VMA flag helpers and convert all mmap_prepare to use them Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 01/12] mm: rename vma_flag_test/set_atomic() to vma_test/set_atomic_flag() Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 02/12] mm: add mk_vma_flags() bitmap flag macro helper Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 03/12] tools: bitmap: add missing bitmap_[subset(), andnot()] Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 04/12] mm: add basic VMA flag operation helper functions Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 05/12] mm: update hugetlbfs to use VMA flags on mmap_prepare Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 06/12] mm: update secretmem " Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 07/12] mm: update shmem_[kernel]_file_*() functions to use vma_flags_t Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 08/12] mm: update all remaining mmap_prepare users " Lorenzo Stoakes
2026-01-20 2:59 ` Zi Yan
2026-01-20 9:01 ` Lorenzo Stoakes
2026-01-22 15:47 ` Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags_t only Lorenzo Stoakes
2026-01-19 23:14 ` Jason Gunthorpe
2026-01-20 9:46 ` Lorenzo Stoakes
2026-01-20 13:36 ` Jason Gunthorpe
2026-01-20 15:10 ` Lorenzo Stoakes
2026-01-20 15:22 ` Jason Gunthorpe
2026-01-20 16:46 ` Lorenzo Stoakes
2026-01-20 16:00 ` Arnd Bergmann
2026-01-20 16:22 ` Lorenzo Stoakes
2026-01-20 16:44 ` Arnd Bergmann
2026-01-20 16:50 ` Lorenzo Stoakes [this message]
2026-01-19 21:19 ` [PATCH RESEND 10/12] tools/testing/vma: separate VMA userland tests into separate files Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 11/12] tools/testing/vma: separate out vma_internal.h into logical headers Lorenzo Stoakes
2026-01-19 21:19 ` [PATCH RESEND 12/12] tools/testing/vma: add VMA userland tests for VMA flag functions Lorenzo Stoakes
2026-01-19 22:31 ` [PATCH RESEND 00/12] mm: add bitmap VMA flag helpers and convert all mmap_prepare to use them Andrew Morton
2026-01-19 23:14 ` Jason Gunthorpe
2026-01-20 9:48 ` Lorenzo Stoakes
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