linux-kernel - Re: [PATCH v3 3/7] mm: Split device-private and coherent folios before freeing

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 for Android: free password hash cracker in your pocket

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

Message-ID: <d1d80b81-678d-4d28-9ac2-95cb74824e73@redhat.com>
Date: Fri, 9 Jan 2026 13:09:17 +0200
From: Mika Penttilä <mpenttil@...hat.com>
To: Francois Dugast <francois.dugast@...el.com>,
 intel-xe@...ts.freedesktop.org
Cc: dri-devel@...ts.freedesktop.org, Matthew Brost <matthew.brost@...el.com>,
 Balbir Singh <balbirs@...dia.com>, Alistair Popple <apopple@...dia.com>,
 Zi Yan <ziy@...dia.com>, David Hildenbrand <david@...nel.org>,
 Oscar Salvador <osalvador@...e.de>, Andrew Morton
 <akpm@...ux-foundation.org>, linux-mm@...ck.org, linux-cxl@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/7] mm: Split device-private and coherent folios
 before freeing

Hi,

On 1/9/26 10:54, Francois Dugast wrote:

> From: Matthew Brost <matthew.brost@...el.com>
>
> Split device-private and coherent folios into individual pages before
> freeing so that any order folio can be formed upon the next use of the
> pages.
>
> Cc: Balbir Singh <balbirs@...dia.com>
> Cc: Alistair Popple <apopple@...dia.com>
> Cc: Zi Yan <ziy@...dia.com>
> Cc: David Hildenbrand <david@...nel.org>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-mm@...ck.org
> Cc: linux-cxl@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Matthew Brost <matthew.brost@...el.com>
> Signed-off-by: Francois Dugast <francois.dugast@...el.com>
> ---
>  mm/memremap.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 63c6ab4fdf08..7289cdd6862f 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -453,6 +453,8 @@ void free_zone_device_folio(struct folio *folio)
>  	case MEMORY_DEVICE_COHERENT:
>  		if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->folio_free))
>  			break;
> +
> +		folio_split_unref(folio);
>  		pgmap->ops->folio_free(folio);
>  		percpu_ref_put_many(&folio->pgmap->ref, nr);
>  		break;

This breaks folio_free implementations like nouveau_dmem_folio_free
which checks the folio order and act upon that.
Maybe add an order parameter to folio_free or let the driver handle the split?

Thanks,
Mika