From: Zi Yan <ziy@nvidia.com>
To: sashiko-reviews@lists.linux.dev
Cc: Shakeel Butt <shakeel.butt@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
"Liam R. Howlett" <liam@infradead.org>,
Matthew Wilcox <willy@infradead.org>,
Suren Baghdasaryan <surenb@google.com>,
Nico Pache <nico.pache@linux.dev>,
Johannes Weiner <hannes@cmpxchg.org>,
Gregory Price <gourry@gourry.net>,
Kairui Song <kasong@tencent.com>,
David Hildenbrand <david@kernel.org>,
Michal Hocko <mhocko@suse.com>,
Alistair Popple <apopple@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Vlastimil Babka <vbabka@kernel.org>,
Lance Yang <lance.yang@linux.dev>,
Lorenzo Stoakes <ljs@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Barry Song <baohua@kernel.org>,
Ryan Roberts <ryan.roberts@arm.com>,
Qi Zheng <qi.zheng@linux.dev>, Dev Jain <dev.jain@arm.com>,
Ying Huang <ying.huang@linux.alibaba.com>,
Usama Arif <usama.arif@linux.dev>,
Mike Rapoport <rppt@kernel.org>, Jan Kara <jack@suse.cz>,
Jonathan Corbet <corbet@lwn.net>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
linux-mm@kvack.org,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
kexec@lists.infradead.org, Masami Hiramatsu <mhiramat@kernel.org>,
Pratyush Yadav <pratyush@kernel.org>,
linux-doc@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
Baoquan He <baoquan.he@linux.dev>,
linux-kernel@vger.kernel.org, Dave Young <ruirui.yang@linux.dev>,
Steven Rostedt <rostedt@goodmis.org>,
Shuah Khan <skhan@linuxfoundation.org>,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v5 17/17] mm/page-flags: remove PG_private
Date: Mon, 21 Sep 2026 11:36:27 -0400 [thread overview]
Message-ID: <E5E3D08D-F0C4-49E4-8763-10CC58FF4260@nvidia.com> (raw)
In-Reply-To: <20260921025520.628971F000FF@smtp.kernel.org>
On 20 Sep 2026, at 22:55, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] mm: silent memory leak masking due to PG_private removal
> --
>
> commit aee12ed3446e69cb6eee57384ca09e768dab36dd
> Author: Zi Yan <ziy@nvidia.com>
>
> mm/page-flags: remove PG_private
>
> This commit removes the PG_private page flag and replaces its usage with
> checking if folio->private != NULL. The space left by PG_private is
> reserved as PG_folio for future use.
>
>> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
>> index 7080a6a1a79e7..b0ddc652e76cc 100644
>> --- a/include/linux/page-flags.h
>> +++ b/include/linux/page-flags.h
> [ ... ]
>> @@ -1169,7 +1175,7 @@ static __always_inline void __ClearPageAnonExclusive(struct page *page)
>> */
>> #define PAGE_FLAGS_CHECK_AT_FREE \
>> (1UL << PG_lru | 1UL << PG_locked | \
>> - 1UL << PG_private | 1UL << PG_private_2 | \
>> + 1UL << PG_private_2 | \
>
> [Severity: Medium]
> Since PG_private is removed from PAGE_FLAGS_CHECK_AT_FREE, does this bypass
> the safety check that ensures a page doesn't have uncleared private data?
>
> Looking at __free_pages_prepare() in mm/page_alloc.c:
>
> page_cpupid_reset_last(page);
> page->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP;
> page->private = 0;
> reset_page_owner(page, order);
>
> The head page's private field is silently zeroed here without any prior
> verification that it was NULL. Previously, free_page_is_bad() would catch
> and report leaked data via a bad_page() warning using
> PAGE_FLAGS_CHECK_AT_FREE.
>
> Now, if a buggy filesystem fails to detach and free folio->private data
> before freeing the page, will this result in silent memory leaks?
Answer copied from RFC:
After the conversion, folio/page should have an elevated refcount whenever
->private is set. That would help detect leaked private data. I tried to
enforce ->private needs to be NULL at page free time[1], but that might
cause trouble for certain use cases.
[1] https://lore.kernel.org/all/20260223032641.1859381-1-ziy@nvidia.com/
>
>> 1UL << PG_writeback | 1UL << PG_reserved | \
>> 1UL << PG_active | \
>> 1UL << PG_unevictable | __PG_MLOCKED | LRU_GEN_MASK)
>
> --
> Sashiko AI review · https://sashiko.dev/#/patchset/20260920-remove-pg_private-v5-0-bb68b6a21869@nvidia.com?part=17
Best Regards,
Yan, Zi
next prev parent reply other threads:[~2026-09-21 15:36 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-21 2:27 [PATCH v5 00/17] Remove PG_private by using page/folio->private checks instead Zi Yan
2026-09-21 2:27 ` [PATCH v5 01/17] mm/zsmalloc: replace PG_private with pointer comparison Zi Yan
2026-09-21 6:02 ` Lance Yang
2026-09-21 2:27 ` [PATCH v5 02/17] perf/ring_buffer: stop using PG_private as AUX page high-order marker Zi Yan
2026-09-21 6:19 ` Lance Yang
2026-09-21 2:27 ` [PATCH v5 03/17] xen/grant-table: stop setting PG_private on pages for grant mapping Zi Yan
2026-09-21 7:00 ` Lance Yang
2026-09-21 2:28 ` [PATCH v5 04/17] fscrypt: stop setting PG_private on bounce page Zi Yan
2026-09-21 7:03 ` Lance Yang
2026-09-21 2:28 ` [PATCH v5 05/17] mm/hugetlb: use direct assignment instead of folio_change_private() Zi Yan
2026-09-21 7:11 ` Lance Yang
2026-09-21 2:28 ` [PATCH v5 06/17] f2fs: stop using PG_private Zi Yan
2026-09-21 7:24 ` Lance Yang
2026-09-21 2:28 ` [PATCH v5 07/17] f2fs: convert the ->private flag helpers to folio-only Zi Yan
2026-09-21 7:39 ` Lance Yang
2026-09-21 2:28 ` [PATCH v5 08/17] erofs: mm/pagemap: add readahead_folio_last() to avoid folio->private Zi Yan
2026-09-21 8:20 ` Lance Yang
2026-09-21 2:28 ` [PATCH v5 09/17] erofs: use folio_attach/detach_private() instead of direct assignment Zi Yan
2026-09-21 8:45 ` Lance Yang
2026-09-21 2:28 ` [PATCH v5 10/17] mm/page-flags: check page/folio->private instead of PG_private Zi Yan
2026-09-21 9:22 ` David Hildenbrand (Arm)
2026-09-21 2:28 ` [PATCH v5 11/17] treewide: remove folio_set/clear_private() usage Zi Yan
2026-09-21 2:28 ` [PATCH v5 12/17] ceph: replace PagePrivate() with page_private() Zi Yan
2026-09-21 2:28 ` [PATCH v5 13/17] md: Use folio_alloc_buffers() Zi Yan
2026-09-21 9:23 ` David Hildenbrand (Arm)
2026-09-21 2:28 ` [PATCH v5 14/17] md: Use folio APIs in free_page() Zi Yan
2026-09-21 2:28 ` [PATCH v5 15/17] md: Remove the last use of page_buffers() Zi Yan
2026-09-21 2:28 ` [PATCH v5 16/17] treewide: remove PagePrivate() and PG_private from comments and docs Zi Yan
2026-09-21 2:28 ` [PATCH v5 17/17] mm/page-flags: remove PG_private Zi Yan
2026-09-21 2:55 ` sashiko-bot
2026-09-21 15:36 ` Zi Yan [this message]
2026-09-21 4:08 ` [PATCH v5 00/17] Remove PG_private by using page/folio->private checks instead Andrew Morton
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