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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1617ac60-6261-483d-aeb5-13aba5f477af@app.fastmail.com>
Date: Tue, 20 Jan 2026 17:00:28 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Lorenzo Stoakes" <lorenzo.stoakes@...cle.com>,
 "Jason Gunthorpe" <jgg@...dia.com>
Cc: "Andrew Morton" <akpm@...ux-foundation.org>,
 "Jarkko Sakkinen" <jarkko@...nel.org>,
 "Dave Hansen" <dave.hansen@...ux.intel.com>,
 "Thomas Gleixner" <tglx@...nel.org>, "Ingo Molnar" <mingo@...hat.com>,
 "Borislav Petkov" <bp@...en8.de>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>,
 "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
 "Dan Williams" <dan.j.williams@...el.com>,
 "Vishal Verma" <vishal.l.verma@...el.com>,
 "Dave Jiang" <dave.jiang@...el.com>,
 "Maarten Lankhorst" <maarten.lankhorst@...ux.intel.com>,
 "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>,
 "Dave Airlie" <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>,
 "Jani Nikula" <jani.nikula@...ux.intel.com>,
 "Joonas Lahtinen" <joonas.lahtinen@...ux.intel.com>,
 "Rodrigo Vivi" <rodrigo.vivi@...el.com>,
 "Tvrtko Ursulin" <tursulin@...ulin.net>,
 Christian König <christian.koenig@....com>,
 "Huang Rui" <ray.huang@....com>, "Matthew Auld" <matthew.auld@...el.com>,
 "Matthew Brost" <matthew.brost@...el.com>,
 "Alexander Viro" <viro@...iv.linux.org.uk>,
 "Christian Brauner" <brauner@...nel.org>, "Jan Kara" <jack@...e.cz>,
 "Benjamin LaHaise" <bcrl@...ck.org>, "Gao Xiang" <xiang@...nel.org>,
 "Chao Yu" <chao@...nel.org>, "Yue Hu" <zbestahu@...il.com>,
 "Jeffle Xu" <jefflexu@...ux.alibaba.com>,
 "Sandeep Dhavale" <dhavale@...gle.com>,
 "Hongbo Li" <lihongbo22@...wei.com>, "Chunhai Guo" <guochunhai@...o.com>,
 "Theodore Ts'o" <tytso@....edu>,
 "Andreas Dilger" <adilger.kernel@...ger.ca>,
 "Muchun Song" <muchun.song@...ux.dev>,
 "Oscar Salvador" <osalvador@...e.de>,
 "David Hildenbrand (Red Hat)" <david@...nel.org>,
 "Konstantin Komarov" <almaz.alexandrovich@...agon-software.com>,
 "Mike Marshall" <hubcap@...ibond.com>,
 "Martin Brandenburg" <martin@...ibond.com>,
 "Tony Luck" <tony.luck@...el.com>,
 "Reinette Chatre" <reinette.chatre@...el.com>,
 "Dave Martin" <Dave.Martin@....com>, "James Morse" <james.morse@....com>,
 "Babu Moger" <babu.moger@....com>, "Carlos Maiolino" <cem@...nel.org>,
 "Damien Le Moal" <dlemoal@...nel.org>,
 "Naohiro Aota" <naohiro.aota@....com>,
 "Johannes Thumshirn" <jth@...nel.org>,
 "Matthew Wilcox" <willy@...radead.org>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 "Vlastimil Babka" <vbabka@...e.cz>, "Mike Rapoport" <rppt@...nel.org>,
 "Suren Baghdasaryan" <surenb@...gle.com>,
 "Michal Hocko" <mhocko@...e.com>, "Hugh Dickins" <hughd@...gle.com>,
 "Baolin Wang" <baolin.wang@...ux.alibaba.com>, "Zi Yan" <ziy@...dia.com>,
 "Nico Pache" <npache@...hat.com>, "Ryan Roberts" <ryan.roberts@....com>,
 "Dev Jain" <dev.jain@....com>, "Barry Song" <baohua@...nel.org>,
 "Lance Yang" <lance.yang@...ux.dev>, "Jann Horn" <jannh@...gle.com>,
 "Pedro Falcato" <pfalcato@...e.de>,
 "David Howells" <dhowells@...hat.com>,
 "Paul Moore" <paul@...l-moore.com>, "James Morris" <jmorris@...ei.org>,
 "Serge E. Hallyn" <serge@...lyn.com>,
 "Yury Norov" <yury.norov@...il.com>,
 "Rasmus Villemoes" <linux@...musvillemoes.dk>, linux-sgx@...r.kernel.org,
 linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev,
 linux-cxl@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 intel-gfx@...ts.freedesktop.org, linux-fsdevel@...r.kernel.org,
 linux-aio@...ck.org, linux-erofs@...ts.ozlabs.org,
 linux-ext4@...r.kernel.org, linux-mm@...ck.org, ntfs3@...ts.linux.dev,
 devel@...ts.orangefs.org, linux-xfs@...r.kernel.org,
 keyrings@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags_t only

On Tue, Jan 20, 2026, at 16:10, Lorenzo Stoakes wrote:
> On Tue, Jan 20, 2026 at 09:36:19AM -0400, Jason Gunthorpe wrote:
>
> I am not sure about this 'idiomatic kernel style' thing either, it feels rather
> conjured. Yes you wouldn't ordinarily pass something larger than a register size
> by-value, but here the intent is for it to be inlined anyway right?
>
> 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:

- functions that cannot be inlined are bound by the ELF ABI, and
  several of them require structs to be passed on the stack regardless
  of the size. Most of the popular architectures seem fine here, but
  mips and powerpc look like they are affected.

- The larger the struct is, the more architectures are affected.
  Parts of the amdgpu driver and the bcachefs file system ran into this
  with 64-bit structures passed by value on 32-bit architectures
  causing horrible codegen even with inlining. I think it's
  usually fine up to a single register size.

- clang's inlining algorithm works the other way round from gcc's:
  inlining into the root caller first and sometimes leaving tiny
  leaf function out of line unless you add __always_inline.

      Arnd