From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C711D38B7D1; Mon, 27 Jul 2026 12:03:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785153820; cv=none; b=tuc7mWWA3KCjnm8BRPVI4pOS+QktZWNFjnSA4/ev7KAByqnukyddDNxVKo1ojaVbUO5NukwVh+xyypvaaJLrTxEpjHD5RQEyUX24CX7luLYfDpfRz2U7qQNj6z06wYvgLIdnm+KSWr1jqlgnsNu2qhH3NHlrgGPLp0c5rvk5TaI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785153820; c=relaxed/simple; bh=yxza4rdkw4/n6IIFAGuKrC+YZcXM3rJkjr83xeAFLLA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lysTWcczXN4KXvxfv+d2YXEDKfSi0eg3GPNhKng21zeDKRV+mC1jVe926Ruvnclp3UATmAi5oe0bHnemdivHMU96MM2f+uQQMVkqWTa00VYbKgX9yZWpu3pPp8s3kwcaP1QbecPXhtJLCzkCfQVQkKFxDHQkiEWfsM2aHzJKur0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OiXA/qnr; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OiXA/qnr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 320A91F000E9; Mon, 27 Jul 2026 12:03:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785153818; bh=xYWQxYr7Z8hEjbx0l6qZmmyZsK1/paY35yOfvBUEJA4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=OiXA/qnrXF+F/T9jW8OrjlLT5fKXKnIHLf7BA+8YmJTwcwQP8TKwWmhs9QRsmcSS0 IRs5bQUDtunXm9LtIyga8PhQHZSYYFun8znmV68wHwZ2xS7SDXDC4+zkEMhx+dSEpA f4fN/OOjlMMEJuEAc277wK0aK9kR3LY+j8llfbFY8uDtIN2DkeVk8ArXr2VbOkQ5Kw z72CrtZ8sBoxPESqYtD1MlGmen/WrsNutp5u+z3NNQ3lJUjDGnOy0mqGXAKzd1+y2u fMF3Gt53MY9JK8lsqKB2jn6QGMxgqLcJkjt2amNK6epwNnSJz63W3WEvB5PNHYrrsh 4UBqnWTWRz0Tg== Date: Mon, 27 Jul 2026 13:03:16 +0100 From: "Lorenzo Stoakes (ARM)" To: Mark Brown Cc: Andrew Morton , David Hildenbrand , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , "Matthew Wilcox (Oracle)" , Jan Kara , Miaohe Lin , Naoya Horiguchi , Rik van Riel , Harry Yoo , Lance Yang , Kees Cook , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Usama Arif , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Peter Xu , Xu Xin , Chengming Zhou , Arnd Bergmann , Greg Kroah-Hartman , 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 Message-ID: References: <20260720-b4-scalable-cow-virt-pgoff-v2-0-2d549757a76f@kernel.org> <20260720-b4-scalable-cow-virt-pgoff-v2-13-2d549757a76f@kernel.org> <9d2c8f26-aaee-459f-b73f-d07d8671e805@sirena.org.uk> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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