linux-kernel - Re: [PATCH v3] mm/page_alloc: clear page->private in free_pages

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Message-ID: <e69270cf-dac1-448c-ace8-3f789e5cdc6e@linux.alibaba.com>
Date: Tue, 10 Feb 2026 09:20:04 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Zi Yan <ziy@...dia.com>, "David Hildenbrand (Arm)" <david@...nel.org>
Cc: Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>, linux-mm@...ck.org,
 akpm@...ux-foundation.org, vbabka@...e.cz, surenb@...gle.com,
 mhocko@...e.com, jackmanb@...gle.com, hannes@...xchg.org, npiggin@...il.com,
 linux-kernel@...r.kernel.org, kasong@...cent.com, hughd@...gle.com,
 chrisl@...nel.org, ryncsn@...il.com, stable@...r.kernel.org,
 willy@...radead.org
Subject: Re: [PATCH v3] mm/page_alloc: clear page->private in
 free_pages_prepare()



On 2/10/26 3:42 AM, Zi Yan wrote:
> On 9 Feb 2026, at 14:39, David Hildenbrand (Arm) wrote:
> 
>> On 2/9/26 18:44, Zi Yan wrote:
>>> On 9 Feb 2026, at 12:36, David Hildenbrand (Arm) wrote:
>>>
>>>> On 2/9/26 17:33, Zi Yan wrote:
>>>>>
>>>>>
>>>>> I agree. Silently fixing non zero ->private just moves the work/responsibility
>>>>> from users to core mm. They could do better. :)
>>>>>
>>>>> We can have a patch or multiple patches to fix users do not zero ->private
>>>>> when freeing a page and add the patch below.
>>>>
>>>> Do we know roughly which ones don't zero it out?
>>>
>>> So far based on [1], I found:
>>>
>>> 1. shmem_swapin_folio() in mm/shmem.c does not zero ->swap.val (overlapping
>>> with private);

After Kairui’s series [1], the shmem part looks good to me. As we no 
longer skip the swapcache now, we shouldn’t clear the ->swap.val of a 
swapcache folio if failed to swap-in.

[1]https://lore.kernel.org/all/20251219195751.61328-1-ryncsn@gmail.com/T/#mcba8a32e1021dc28ce1e824c9d042dca316a30d7

>>> 2. __free_slab() in mm/slub.c does not zero ->inuse, ->objects, ->frozen
>>> (overlapping with private).
>>>
>>> Mikhail found ttm_pool_unmap_and_free() in drivers/gpu/drm/ttm/ttm_pool.c
>>> does not zero ->private, which stores page order.