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

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Message-ID: <3b95bb12-5642-443b-b163-8b5f5f6400c4@kernel.org>
Date: Mon, 9 Feb 2026 17:06:40 +0100
From: "David Hildenbrand (Arm)" <david@...nel.org>
To: Zi Yan <ziy@...dia.com>
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 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.

-- 
Cheers,

David