From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: Mark Brown <broonie@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
"Liam R. Howlett" <liam@infradead.org>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>, Jann Horn <jannh@google.com>,
Pedro Falcato <pfalcato@suse.de>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Jan Kara <jack@suse.cz>, Miaohe Lin <linmiaohe@huawei.com>,
Naoya Horiguchi <nao.horiguchi@gmail.com>,
Rik van Riel <riel@surriel.com>, Harry Yoo <harry@kernel.org>,
Lance Yang <lance.yang@linux.dev>, Kees Cook <kees@kernel.org>,
Zi Yan <ziy@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Nico Pache <npache@redhat.com>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>,
Usama Arif <usama.arif@linux.dev>,
Matthew Brost <matthew.brost@intel.com>,
Joshua Hahn <joshua.hahnjy@gmail.com>,
Rakie Kim <rakie.kim@sk.com>, Byungchul Park <byungchul@sk.com>,
Gregory Price <gourry@gourry.net>,
Ying Huang <ying.huang@linux.alibaba.com>,
Alistair Popple <apopple@nvidia.com>,
Peter Xu <peterx@redhat.com>, Xu Xin <xu.xin16@zte.com.cn>,
Chengming Zhou <chengming.zhou@linux.dev>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v2 13/15] mm/vma: make MAP_PRIVATE-mapped /dev/zero mappings truly anonymous
Date: Mon, 27 Jul 2026 13:03:16 +0100 [thread overview]
Message-ID: <amdI42D5Y_nsB1t_@lucifer> (raw)
In-Reply-To: <9d2c8f26-aaee-459f-b73f-d07d8671e805@sirena.org.uk>
On Mon, Jul 27, 2026 at 12:48:57PM +0100, Mark Brown wrote:
> On Mon, Jul 20, 2026 at 03:38:39PM +0100, Lorenzo Stoakes (ARM) wrote:
> > When mapping /dev/zero with MAP_PRIVATE, one ends up with strange VMAs
> > originating from Linux's distant past.
> >
> > These have vma->vm_file set but NULL vma->vm_ops, meaning they satisfy
> > vma_is_anonymous() but otherwise resemble a file-backed VMA.
>
> I'm seeing a test failure in the proc proc-self-map-files-0002 kselftest
> which bisects to this change in -next. The test just says:
>
> # selftests: proc: proc-self-map-files-002
> not ok 11 selftests: proc: proc-self-map-files-002 # exit=1
>
> which isn't super informative. Full log at:
>
> https://lava.sirena.org.uk/scheduler/job/3030495#L13846
Thanks, will investigate!
It's likely making some assumptions that no longer apply about MAP_PRIVATE-/dev/zero mappings here.
>
> bisect log:
>
> # bad: [c5e32e86ca02b003f86e095d379b38148999293d] Add linux-next specific files for 20260726
> # good: [692519a077bfb1a66d209e713d2210bb1d9adcaf] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git
> # good: [ef4f2357df6e9dd6213ce00d01253f3c458d5df0] regmap: clean up kernel-doc comments
> # good: [86e9ba573c353afd1a46816682f4cc3dbabeeb23] irqchip/irq-imgpdc: Remove unused driver
> git bisect start 'c5e32e86ca02b003f86e095d379b38148999293d' '692519a077bfb1a66d209e713d2210bb1d9adcaf' 'ef4f2357df6e9dd6213ce00d01253f3c458d5df0' '86e9ba573c353afd1a46816682f4cc3dbabeeb23'
> # test job: [ef4f2357df6e9dd6213ce00d01253f3c458d5df0] https://lava.sirena.org.uk/scheduler/job/3020719
> # test job: [86e9ba573c353afd1a46816682f4cc3dbabeeb23] https://lava.sirena.org.uk/scheduler/job/2955047
> # test job: [c5e32e86ca02b003f86e095d379b38148999293d] https://lava.sirena.org.uk/scheduler/job/3030495
> # bad: [c5e32e86ca02b003f86e095d379b38148999293d] Add linux-next specific files for 20260726
> git bisect bad c5e32e86ca02b003f86e095d379b38148999293d
> # test job: [673a43d4e283e8fc3bee7a874766278427263bc1] https://lava.sirena.org.uk/scheduler/job/3030777
> # bad: [673a43d4e283e8fc3bee7a874766278427263bc1] Merge branch 'libcrypto-next' of https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git
> git bisect bad 673a43d4e283e8fc3bee7a874766278427263bc1
> # test job: [5dd91aac4216c19e9eeea6e0c1a04bcb3e43a876] https://lava.sirena.org.uk/scheduler/job/3031099
> # bad: [5dd91aac4216c19e9eeea6e0c1a04bcb3e43a876] Merge branch 'xtensa-for-next' of https://github.com/jcmvbkbc/linux-xtensa.git
> git bisect bad 5dd91aac4216c19e9eeea6e0c1a04bcb3e43a876
> # test job: [457b365bc545636d75f65067d18afa86f6ced162] https://lava.sirena.org.uk/scheduler/job/3031248
> # bad: [457b365bc545636d75f65067d18afa86f6ced162] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git
> git bisect bad 457b365bc545636d75f65067d18afa86f6ced162
> # test job: [a8fa5c7be42a37866fcc315470df3307f0583c47] https://lava.sirena.org.uk/scheduler/job/3031351
> # good: [a8fa5c7be42a37866fcc315470df3307f0583c47] mm/vma: update create_init_stack_vma() to use vma_flags_t
> git bisect good a8fa5c7be42a37866fcc315470df3307f0583c47
> # test job: [5c9f41c7115f0e16b7e133abca791a4860bee0b6] https://lava.sirena.org.uk/scheduler/job/3031429
> # bad: [5c9f41c7115f0e16b7e133abca791a4860bee0b6] Merge branch 'kbuild-for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux.git
> git bisect bad 5c9f41c7115f0e16b7e133abca791a4860bee0b6
> # test job: [c68210527d235e59afa54bc6aba6ecc532488a82] https://lava.sirena.org.uk/scheduler/job/3031482
> # bad: [c68210527d235e59afa54bc6aba6ecc532488a82] mm: page_alloc: fix non-movable reclaim storm in defrag_mode
> git bisect bad c68210527d235e59afa54bc6aba6ecc532488a82
> # test job: [497078da29fbfe6ae057c020f1e5717ded142471] https://lava.sirena.org.uk/scheduler/job/3031540
> # good: [497078da29fbfe6ae057c020f1e5717ded142471] mm/huge_memory: fold split_folio_to_list_to_order() into split_folio_to_order()
> git bisect good 497078da29fbfe6ae057c020f1e5717ded142471
> # test job: [2afd297a9a621ad41892bc0a05481110f46ebfc2] https://lava.sirena.org.uk/scheduler/job/3031619
> # bad: [2afd297a9a621ad41892bc0a05481110f46ebfc2] tools/testing/vma: add test to assert MAP_PRIVATE-/dev/zero is anon
> git bisect bad 2afd297a9a621ad41892bc0a05481110f46ebfc2
> # test job: [a4beb459e21af80c1d8c37b079686753c21932ca] https://lava.sirena.org.uk/scheduler/job/3031661
> # good: [a4beb459e21af80c1d8c37b079686753c21932ca] mm/vma: introduce VMA virtual page offset field and add helpers
> git bisect good a4beb459e21af80c1d8c37b079686753c21932ca
> # test job: [84bd1aceb0233c3de9064028d31a16ecf50070d9] https://lava.sirena.org.uk/scheduler/job/3031711
> # good: [84bd1aceb0233c3de9064028d31a16ecf50070d9] mm/rmap: track whether the page VMA mapped walk is anonymous
> git bisect good 84bd1aceb0233c3de9064028d31a16ecf50070d9
> # test job: [880b6fe7442df760fe0a726b5f5e568bc6b450b6] https://lava.sirena.org.uk/scheduler/job/3031752
> # good: [880b6fe7442df760fe0a726b5f5e568bc6b450b6] tools/testing/vma: expand VMA merge tests to assert virt pgoff
> git bisect good 880b6fe7442df760fe0a726b5f5e568bc6b450b6
> # test job: [e2ad1c5a1f0a96a4a0435213b0a5cb963dc501c5] https://lava.sirena.org.uk/scheduler/job/3031804
> # good: [e2ad1c5a1f0a96a4a0435213b0a5cb963dc501c5] mm/vma: only permit MAP_PRIVATE /dev/zero to be mapped anonymous
> git bisect good e2ad1c5a1f0a96a4a0435213b0a5cb963dc501c5
> # test job: [9f2782812095787d87ee6b742899ae37966ef0f5] https://lava.sirena.org.uk/scheduler/job/3031854
> # bad: [9f2782812095787d87ee6b742899ae37966ef0f5] mm/vma: make MAP_PRIVATE-mapped /dev/zero mappings truly anonymous
> git bisect bad 9f2782812095787d87ee6b742899ae37966ef0f5
> # first bad commit: [9f2782812095787d87ee6b742899ae37966ef0f5] mm/vma: make MAP_PRIVATE-mapped /dev/zero mappings truly anonymous
Cheers, Lorenzo
next prev parent reply other threads:[~2026-07-27 12:03 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-20 14:38 [PATCH v2 00/15] mm/rmap: index MAP_PRIVATE file-backed folios by virt pgoff Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 01/15] mm/vma: introduce VMA virtual page offset field and add helpers Lorenzo Stoakes (ARM)
2026-07-20 15:49 ` Gregory Price
2026-07-20 16:56 ` Lorenzo Stoakes (ARM)
2026-07-20 17:26 ` Gregory Price
2026-07-27 12:03 ` Lorenzo Stoakes (ARM)
2026-07-25 8:08 ` xu.xin16
2026-07-20 14:38 ` [PATCH v2 02/15] mm: introduce linear_virt_page_index() Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 03/15] mm: abstract vma_address() and introduce vma_anon_address() Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 04/15] mm: update print_bad_page_map() to show virtual page index Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 05/15] mm: introduce and use vma_filebacked_address() Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 06/15] mm: propagate VMA virtual page offset on map, remap, split + merge Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 07/15] mm/rmap: track whether the page VMA mapped walk is anonymous Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 08/15] mm: introduce and use linear_folio_page_index() Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 09/15] mm/rmap: use virt pgoff for MAP_PRIVATE file-backed anon folios Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 10/15] tools/testing/vma: expand VMA merge tests to assert virt pgoff Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 11/15] tools/testing/selftests/mm: test virtual page offset merge behaviour Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 12/15] mm/vma: only permit MAP_PRIVATE /dev/zero to be mapped anonymous Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 13/15] mm/vma: make MAP_PRIVATE-mapped /dev/zero mappings truly anonymous Lorenzo Stoakes (ARM)
2026-07-27 11:48 ` Mark Brown
2026-07-27 12:03 ` Lorenzo Stoakes (ARM) [this message]
2026-07-20 14:38 ` [PATCH v2 14/15] tools/testing/vma: add test to assert MAP_PRIVATE-/dev/zero is anon Lorenzo Stoakes (ARM)
2026-07-20 14:38 ` [PATCH v2 15/15] tools/testing/selftests/mm: add MAP_PRIVATE-/dev/zero merge tests Lorenzo Stoakes (ARM)
2026-07-20 19:48 ` [PATCH v2 00/15] mm/rmap: index MAP_PRIVATE file-backed folios by virt pgoff Andrew Morton
2026-07-27 12:04 ` Lorenzo Stoakes (ARM)
2026-07-27 14:44 ` David Hildenbrand (Arm)
2026-07-27 15:57 ` Lorenzo Stoakes (ARM)
2026-07-27 15:59 ` Matthew Wilcox
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