linux-kernel - Re: [v5 01/15] mm/zone_device: support large zone device private folios

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Message-ID: <244005a2-4796-4985-853e-f916bdfd096a@redhat.com>
Date: Thu, 11 Sep 2025 14:52:08 +0200
From: David Hildenbrand <david@...hat.com>
To: Balbir Singh <balbirs@...dia.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Cc: damon@...ts.linux.dev, dri-devel@...ts.freedesktop.org,
 Andrew Morton <akpm@...ux-foundation.org>, Zi Yan <ziy@...dia.com>,
 Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
 Byungchul Park <byungchul@...com>, Gregory Price <gourry@...rry.net>,
 Ying Huang <ying.huang@...ux.alibaba.com>,
 Alistair Popple <apopple@...dia.com>, Oscar Salvador <osalvador@...e.de>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Lyude Paul <lyude@...hat.com>,
 Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Ralph Campbell <rcampbell@...dia.com>,
 Mika Penttilä <mpenttil@...hat.com>,
 Matthew Brost <matthew.brost@...el.com>,
 Francois Dugast <francois.dugast@...el.com>
Subject: Re: [v5 01/15] mm/zone_device: support large zone device private
 folios

On 11.09.25 14:49, Balbir Singh wrote:
> On 9/11/25 21:45, David Hildenbrand wrote:
>> On 08.09.25 02:04, Balbir Singh wrote:
>>> Add routines to support allocation of large order zone device folios
>>> and helper functions for zone device folios, to check if a folio is
>>> device private and helpers for setting zone device data.
>>>
>>> When large folios are used, the existing page_free() callback in
>>> pgmap is called when the folio is freed, this is true for both
>>> PAGE_SIZE and higher order pages.
>>>
>>> Zone device private large folios do not support deferred split and
>>> scan like normal THP folios.
>>>
>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>> Cc: David Hildenbrand <david@...hat.com>
>>> Cc: Zi Yan <ziy@...dia.com>
>>> Cc: Joshua Hahn <joshua.hahnjy@...il.com>
>>> Cc: Rakie Kim <rakie.kim@...com>
>>> Cc: Byungchul Park <byungchul@...com>
>>> Cc: Gregory Price <gourry@...rry.net>
>>> Cc: Ying Huang <ying.huang@...ux.alibaba.com>
>>> Cc: Alistair Popple <apopple@...dia.com>
>>> Cc: Oscar Salvador <osalvador@...e.de>
>>> Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
>>> Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
>>> Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>
>>> Cc: Nico Pache <npache@...hat.com>
>>> Cc: Ryan Roberts <ryan.roberts@....com>
>>> Cc: Dev Jain <dev.jain@....com>
>>> Cc: Barry Song <baohua@...nel.org>
>>> Cc: Lyude Paul <lyude@...hat.com>
>>> Cc: Danilo Krummrich <dakr@...nel.org>
>>> Cc: David Airlie <airlied@...il.com>
>>> Cc: Simona Vetter <simona@...ll.ch>
>>> Cc: Ralph Campbell <rcampbell@...dia.com>
>>> Cc: Mika Penttilä <mpenttil@...hat.com>
>>> Cc: Matthew Brost <matthew.brost@...el.com>
>>> Cc: Francois Dugast <francois.dugast@...el.com>
>>>
>>> Signed-off-by: Balbir Singh <balbirs@...dia.com>
>>> ---
>>
>> You missed my comments of this patch in v3.
>>
> 
> Hi, David
> 
> Looks I missed your comments, just checked those were largely about alignment and
> integrating the code for DEVICE_COHERENT and DEVICE_PRIVATE cases into similar looking
> bits for zone device folio free and code-alignment. I'll take a look and update as needed.

Yes, and the confusing folio->mapping = NULL that I cannot connect to 
THP support.

-- 
Cheers

David / dhildenb