linux-kernel - Re: [PATCH RFC 07/29] mm/migrate: rename isolate_movable_page() to isolate_movable_ops

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: <878qlaqc4k.fsf@DESKTOP-5N7EMDA>
Date: Mon, 30 Jun 2025 08:58:03 +0800
From: "Huang, Ying" <ying.huang@...ux.alibaba.com>
To: Alistair Popple <apopple@...dia.com>
Cc: David Hildenbrand <david@...hat.com>,  Zi Yan <ziy@...dia.com>,  Matthew
 Wilcox <willy@...radead.org>,  linux-kernel@...r.kernel.org,
  linux-mm@...ck.org,  linux-doc@...r.kernel.org,
  linuxppc-dev@...ts.ozlabs.org,  virtualization@...ts.linux.dev,
  linux-fsdevel@...r.kernel.org,  Andrew Morton
 <akpm@...ux-foundation.org>,  Jonathan Corbet <corbet@....net>,  Madhavan
 Srinivasan <maddy@...ux.ibm.com>,  Michael Ellerman <mpe@...erman.id.au>,
  Nicholas Piggin <npiggin@...il.com>,  Christophe Leroy
 <christophe.leroy@...roup.eu>,  Jerrin Shaji George
 <jerrin.shaji-george@...adcom.com>,  Arnd Bergmann <arnd@...db.de>,  Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>,  "Michael S. Tsirkin"
 <mst@...hat.com>,  Jason Wang <jasowang@...hat.com>,  Xuan Zhuo
 <xuanzhuo@...ux.alibaba.com>,  Eugenio Pérez
 <eperezma@...hat.com>,
  Alexander Viro <viro@...iv.linux.org.uk>,  Christian Brauner
 <brauner@...nel.org>,  Jan Kara <jack@...e.cz>,  Matthew Brost
 <matthew.brost@...el.com>,  Joshua Hahn <joshua.hahnjy@...il.com>,  Rakie
 Kim <rakie.kim@...com>,  Byungchul Park <byungchul@...com>,  Gregory Price
 <gourry@...rry.net>,  Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,  "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>,  Minchan Kim <minchan@...nel.org>,
  Sergey Senozhatsky <senozhatsky@...omium.org>,  Brendan Jackman
 <jackmanb@...gle.com>,  Johannes Weiner <hannes@...xchg.org>,  Jason
 Gunthorpe <jgg@...pe.ca>,  John Hubbard <jhubbard@...dia.com>,  Peter Xu
 <peterx@...hat.com>,  Xu Xin <xu.xin16@....com.cn>,  Chengming Zhou
 <chengming.zhou@...ux.dev>,  Miaohe Lin <linmiaohe@...wei.com>,  Naoya
 Horiguchi <nao.horiguchi@...il.com>,  Oscar Salvador <osalvador@...e.de>,
  Rik van Riel <riel@...riel.com>,  Harry Yoo <harry.yoo@...cle.com>,  Qi
 Zheng <zhengqi.arch@...edance.com>,  Shakeel Butt <shakeel.butt@...ux.dev>
Subject: Re: [PATCH RFC 07/29] mm/migrate: rename isolate_movable_page() to
 isolate_movable_ops_page()

Alistair Popple <apopple@...dia.com> writes:

> On Sun, Jun 29, 2025 at 07:28:50PM +0800, Huang, Ying wrote:
>> David Hildenbrand <david@...hat.com> writes:
>> 
>> > On 18.06.25 20:48, Zi Yan wrote:
>> >> On 18 Jun 2025, at 14:39, Matthew Wilcox wrote:
>> >> 
>> >>> On Wed, Jun 18, 2025 at 02:14:15PM -0400, Zi Yan wrote:
>> >>>> On 18 Jun 2025, at 13:39, David Hildenbrand wrote:
>> >>>>
>> >>>>> ... and start moving back to per-page things that will absolutely not be
>> >>>>> folio things in the future. Add documentation and a comment that the
>> >>>>> remaining folio stuff (lock, refcount) will have to be reworked as well.
>> >>>>>
>> >>>>> While at it, convert the VM_BUG_ON() into a WARN_ON_ONCE() and handle
>> >>>>> it gracefully (relevant with further changes), and convert a
>> >>>>> WARN_ON_ONCE() into a VM_WARN_ON_ONCE_PAGE().
>> >>>>
>> >>>> The reason is that there is no upstream code, which use movable_ops for
>> >>>> folios? Is there any fundamental reason preventing movable_ops from
>> >>>> being used on folios?
>> >>>
>> >>> folios either belong to a filesystem or they are anonymous memory, and
>> >>> so either the filesystem knows how to migrate them (through its a_ops)
>> >>> or the migration code knows how to handle anon folios directly.
>> >
>> > Right, migration of folios will be handled by migration core.
>> >
>> >> for device private pages, to support migrating >0 order anon or fs
>> >> folios
>> >> to device, how should we represent them for devices? if you think folio is
>> >> only for anon and fs.
>> >
>> > I assume they are proper folios, so yes. Just like they are handled
>> > today (-> folios)
>
> Yes, they should be proper folios.

So, folios include file cache, anonymous, and some device private.

>> > I was asking a related question at LSF/MM in Alistair's session: are
>> > we sure these things will be folios even before they are assigned to a
>> > filesystem? I recall the answer was "yes".
>> >
>> > So we don't (and will not) support movable_ops for folios.
>> 
>> Is it possible to use some device specific callbacks (DMA?) to copy
>> from/to the device private folios (or pages) to/from the normal
>> file/anon folios in the future?
>
> I guess we could put such callbacks on the folio->pgmap, but I'm not sure why
> we would want to. Currently all migration to/from device private (or coherent)
> folios is managed by the device, which is one of the features of ZONE_DEVICE.

Yes.  The is the current behavior per my understanding too.

> Did you have some particular reason/idea for why we might want to do this?

No.  Just want to check whether there are some requirements for that.  I
think that it's just another way to organize code.

---
Best Regards,
Huang, Ying