From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 816B2C79FA1 for ; Mon, 7 Sep 2026 16:21:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7726F6B00A4; Mon, 7 Sep 2026 12:21:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7234B6B00A5; Mon, 7 Sep 2026 12:21:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5EAE86B00A6; Mon, 7 Sep 2026 12:21:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 33F5F6B00A4 for ; Mon, 7 Sep 2026 12:21:38 -0400 (EDT) Received: from smtpin11.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id B83731401EC for ; Mon, 7 Sep 2026 16:21:37 +0000 (UTC) X-FDA: 85187481834.11.B7B93CC Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf24.hostedemail.com (Postfix) with ESMTP id 091AB18000F for ; Mon, 7 Sep 2026 16:21:35 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WioyDUTT; spf=pass (imf24.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788798096; b=xAS1cnCVWkaOCW+384pzVaAhOD32BS9hgv+HFMpCtCgeUUkVzuBqFfetGzvRODSBatgjfj +prevgMfzkgn2v/sUFZgv4R/e3ssM4YtP811xCT3wtitJd1mgep2abIAWr0c2/VBPoT3Ux 5qvsv4UlhG3n1ITyzOekcXh1ETkSnKE= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WioyDUTT; spf=pass (imf24.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788798096; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=1FcNaC3tk4BXA1Rw0dktdlxAia8YznUdS4WNauHXOFY=; b=iAfwc7/KTcrHlf+ioSlnSW9vNxSwp2HEg/nll5payunj3/vYpAAcvkSl7Dabo4ccDIcUUP rqyqh+ae8Wi4gqWE1xwtC1OqdrDkYNb1F7MQAk5wlkNZ2sXbrv++nf+NGuIAZTBrA3Ob31 UJidfYebcOMoOSXCfpCqVSCO9P2vX9U= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 8BD5E601DB; Mon, 7 Sep 2026 16:21:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F4641F00A3E; Mon, 7 Sep 2026 16:21:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788798095; bh=1FcNaC3tk4BXA1Rw0dktdlxAia8YznUdS4WNauHXOFY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=WioyDUTTj2SiZw9LN5ke28ZFLliBYvU9wN/q0/x+LOXIMH7mcf/0D27FC7YFtJeKK ESRHLr22hys2gbj0GZXm6i5sPjXSobpyGsHbKEy4X5VdOOSBZoaNPmaJJ0B+JKdl7x bOlo1MY6Am+P+mVK1amJkr0tl/iNAmL8sllqLqxB4g4qdAoz0UnpLuxs1bxh7X7cNw L/N5EOxXwQ468K8MQsNbEJEy2xqeCIjMI/5O0xK4u4p0DeqNJchIatLOLoVAXGTIEv sLyn1+/KK8yns9tOK72XsILWbA2QWSAoL6rrJSMBJake+IyZPgb02XvITcPjEATZ3+ kN9cnET569djA== Message-ID: <292b27a7-94d1-4a2e-8346-a53e80fd2ed0@kernel.org> Date: Mon, 7 Sep 2026 18:21:27 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/6] mm: implement file_is_dev_zero() to uniquely identify /dev/zero To: "Lorenzo Stoakes (ARM)" , Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Hugh Dickins , Baolin Wang , "Matthew Wilcox (Oracle)" , Jan Kara Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20260902-map-private-dev-zero-v1-0-a578c730cec7@kernel.org> <20260902-map-private-dev-zero-v1-2-a578c730cec7@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260902-map-private-dev-zero-v1-2-a578c730cec7@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 091AB18000F X-Stat-Signature: 4uhjydpidtn6wkw14xb9amw76cuyxxsu X-HE-Tag: 1788798095-72715 X-HE-Meta: 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 nWMIFVwV vsefPkvKfT4VuQQWfqJNWcuWUwXO+vTR5U23cwwLRYFa9QHKbwWjJ2J/McJ8VQrO6CaMN0zS7Lue33hcIodZgDYXpZL0/LRJdfdIkGvnY92KnLVqhQOWkIDKfAn3eehsPmuIXCWuqCmQD7R/ze904HYJPc2FTI/h6J3p91RvZXwAZL/lPpKvXeKMNZbc4RZkBgbVk5ZquvW98t6dMqUCYTi4QWzhA+8cqM9dTtNIFn3FSox3BoCKEcTeX63s5X98+ldlQYRUdKMnlJSKzXAgt8zhsUMFAtn0X2lrRIeE9/WzVEbOmZEHdEBLlAbZTsHfa9HrIYZfWNg7iReg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/2/26 20:00, Lorenzo Stoakes (ARM) wrote: > To lay the foundation for a future change that converts > MAP_PRIVATE-/dev/zero mappings to be truly anonymous, add the ability to > uniquely identify these mappings. > > With the memory character device now part of mm/ this is trivially > achievable through a file_is_dev_zero() predicate that simply tests that > the file operation hooks are zero_fops. > > Also update userland VMA tests to expose file_is_dev_zero() and provide > a stub zero_fops for testing. > > Signed-off-by: Lorenzo Stoakes (ARM) > --- yes! Acked-by: David Hildenbrand (Arm) -- Cheers, David