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

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Message-ID: <3594E090-CA8C-4726-9738-5F445092DD61@nvidia.com>
Date: Mon, 09 Feb 2026 11:08:47 -0500
From: Zi Yan <ziy@...dia.com>
To: "David Hildenbrand (Arm)" <david@...nel.org>
Cc: Vlastimil Babka <vbabka@...e.cz>,
 Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>, linux-mm@...ck.org,
 akpm@...ux-foundation.org, 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 9 Feb 2026, at 11:06, David Hildenbrand (Arm) wrote:

> On 2/9/26 17:05, Zi Yan wrote:
>> On 9 Feb 2026, at 11:03, David Hildenbrand (Arm) wrote:
>>
>>> On 2/9/26 17:00, Zi Yan wrote:
>>>>
>>>>
>>>> Currently, _mm_id (_mm_ids) overlaps with page->private. At split time,
>>>> it should be MM_ID_DUMMY (0), so page->private should be 0 all time.
>>>
>>> Yes, it's designed like that; because that check here caught it during development :)
>>>
>>>>
>>>>
>>>> It is still better to have the check and fix in place. Why do we want to
>>>> skip device private folio?
>>>
>>> I don't understand the question, can you elaborate?
>>
>> You said,
>> “BTW, I wonder whether we should bring that check back for non-device folios.”
>>
>> I thought you know why device folio needs to keep ->private not cleared during
>> split.
>
> Oh, I thought there was some overlay of ->private with zone-device special stuff. But I checked the structs and didn't spot it immediately. So I ended up asking Balbir as reply to his latest series that got merged.

Got it. We will bring it back once we hear back from Balbir. Thanks.

Best Regards,
Yan, Zi