From: "David Hildenbrand (Arm)" <david@kernel.org>
To: "Christian König" <christian.koenig@amd.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Zi Yan" <ziy@nvidia.com>
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Subject: Re: [PATCH v1 00/11] Zero page->private when freeing pages
Date: Mon, 23 Feb 2026 16:27:09 +0100 [thread overview]
Message-ID: <61e2acbc-d3c7-424a-80da-3c34a593c9ad@kernel.org> (raw)
In-Reply-To: <da2f5f7c-0252-4085-a490-a505d0169bc4@amd.com>
On 2/23/26 16:22, Christian König wrote:
> On 2/23/26 15:14, David Hildenbrand (Arm) wrote:
>> On 2/23/26 15:06, Christian König wrote:
>>>
>>> Completely agree. This is just asking for trouble.
>>>
>>> The cache line(s) backing this struct page are most likely accessed anyway on free/alloc. So I don't see much extra overhead.
>>
>> I think the question is more around handling non-head pages when freeing larger orders. But maybe the overhead of zeroing page->private it there as well in __free_pages_prepare() is tolerable.
>
> Good point, sounds like that is a bit more than I thought it would be.
Right. We already iterate over all "tail" pages in
__free_pages_prepare() to clear page flags
(page + i)->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP;
Maybe zeroing page->private there is not too bad.
>
>> I'll note, though, that we already require page->mapping and page->memcg_data of pages to be zeroed by the caller, so it's not completely crazy. (see page_expected_state)
>
> Well that's not defensive at all, basically everybody which forgets to do that can cause hard to debug trouble. Maybe that practice should be reconsidered.
Right, we do have check_pages= to activate the page_expected_state()
checks, where we will detect such problems.
(including the mapcount being -1 etc.)
--
Cheers,
David
prev parent reply other threads:[~2026-02-23 15:27 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-23 3:26 Zi Yan
2026-02-23 3:26 ` [PATCH v1 01/11] relay: zero " Zi Yan
2026-02-23 14:45 ` Usama Arif
2026-02-23 3:26 ` [PATCH v1 02/11] mm/slub: " Zi Yan
2026-02-23 3:26 ` [PATCH v1 03/11] drm/ttm: " Zi Yan
2026-02-23 10:43 ` Christian König
2026-02-23 3:26 ` [PATCH v1 04/11] blk-mq: " Zi Yan
2026-02-23 3:26 ` [PATCH v1 05/11] watch_queue: " Zi Yan
2026-02-23 3:26 ` [PATCH v1 06/11] binder: " Zi Yan
2026-02-23 3:26 ` [PATCH v1 07/11] null_blk: " Zi Yan
2026-02-23 3:26 ` [PATCH v1 08/11] percpu: " Zi Yan
2026-02-23 3:26 ` [PATCH v1 09/11] erofs: " Zi Yan
2026-02-23 3:26 ` [PATCH v1 10/11] mm/huge_memory: add page->private check back in __split_folio_to_order() Zi Yan
2026-02-23 3:26 ` [PATCH v1 11/11] mm/page_alloc: check page->private upon page free Zi Yan
2026-02-23 4:28 ` [PATCH v1 00/11] Zero page->private when freeing pages Matthew Wilcox
2026-02-23 9:36 ` David Hildenbrand (Arm)
2026-02-23 8:40 ` [syzbot ci] " syzbot ci
2026-02-23 13:46 ` [PATCH v1 00/11] " Christoph Hellwig
2026-02-23 14:00 ` Zi Yan
2026-02-23 14:03 ` Christoph Hellwig
2026-02-23 14:11 ` Zi Yan
2026-02-23 14:06 ` Christian König
2026-02-23 14:14 ` David Hildenbrand (Arm)
2026-02-23 15:22 ` Christian König
2026-02-23 15:27 ` David Hildenbrand (Arm) [this message]
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