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 D2FBBCA5FCB for ; Thu, 1 Oct 2026 11:33:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BB0B06B0088; Thu, 1 Oct 2026 07:33:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B61196B008A; Thu, 1 Oct 2026 07:33:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A767D6B008C; Thu, 1 Oct 2026 07:33:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 82AF16B0088 for ; Thu, 1 Oct 2026 07:33:15 -0400 (EDT) Received: from smtpin11.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id ECC09C03C1 for ; Thu, 1 Oct 2026 11:33:14 +0000 (UTC) X-FDA: 85273846308.11.9354283 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf20.hostedemail.com (Postfix) with ESMTP id 324461C000B for ; Thu, 1 Oct 2026 11:33:13 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=iD53Oifp; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790854393; 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=b2hY2Lwa9e4ug6tiGWzP7cLmTEKbjt1EVVbwD8WgJqc=; b=tU78WWvD2vWONlXmpwzGuIZDBhgxrJSRCvnB3Y9lnu96vkqlZFi5O8kadjktdAAe6EVcJl m9lOSK5c0U+x9vxjVKNfMFKYr9deZYlIzjfVT3065d1oUvRBITA8kKQPMh/1ww37oH/Xqp AtVIfXac1g1416/w2T/4yqTJtUpS+Dg= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=iD53Oifp; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790854393; b=wLnR5s930a43HBwey4OSB/s165QPSeRUOHl+Uf+f1tw5thoLVOG/Y6NPgTPkkTmNTi+7fr wIjIQC3gGfvwYtKWjMsyAEmBf+gvxa21NxJJHQV2sATmJDbEFCuZ2KTTzbf93hJNnWUgus 2iRamoryNQkH/hV7BP/3bh6jodQff8w= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id B306360A55; Thu, 1 Oct 2026 11:33:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3039A1F000FF; Thu, 1 Oct 2026 11:33:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790854392; bh=b2hY2Lwa9e4ug6tiGWzP7cLmTEKbjt1EVVbwD8WgJqc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=iD53Oifp/0W8HMOSNW9RLwVbugDqNyDtJoq4TPv4O2H+BOf7+CcJKqPB1nG0G9tg4 Ou+C2O2JlfDb7vpzb7HfDkraQyJ++Upwa8X8TTgcD6F+Ze956QW97elz7kK4l/gbzY SWdxBw6KMHjiH6PnnGJhkq1Sjz751s1sMCP4N/GD1rEBqE5j4tjvdsDniB+5d5JStZ ygajxJTAvJFlo/QWoLABdpjnQ0OIGs1pIeksWHX1R8jWoMvp1fKOpKwMd24oe1/GeU MfPXizuEjQRxBTnxQy6GWVhaO3YwSTyWDkV6mriRPMOVVa1Xc9P2kVv7Wefp7PZRR7 /qs2Z/i1dQ5zA== Message-ID: <7454d7a3-57c6-4883-a66b-26129e633c6e@kernel.org> Date: Thu, 1 Oct 2026 13:33:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/7] maccess: Use a scoped guard for page faults To: Muhammad Usama Anjum Cc: Catalin Marinas , Will Deacon , Mark Rutland , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" , open list , "open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)" , "open list:MEMORY MANAGEMENT - CORE" , Viktor Malik References: <20260824160523.3907021-1-usama.anjum@arm.com> <20260824160523.3907021-5-usama.anjum@arm.com> <79daa73b-0d34-4e84-8450-56f90bc700d4@kernel.org> <98e9ac67-7df3-4c0a-8814-37e196d94020@arm.com> 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: <98e9ac67-7df3-4c0a-8814-37e196d94020@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 324461C000B X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: znqgwfic3wefdmq3d5yc1rzsq8d9t8pw X-HE-Tag: 1790854393-9296 X-HE-Meta: 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 +G+vxOGT 7S1pRjrBxGMangbi+Iwf0XZpTQNxsrgAApMAubFW5kH74w316koyMUavqNlA6aGMBCL6RKrPttI2/6JIVcLUMjA4SSjprF7Axnc+RGCCJEcXUuCim1o8gjhTSL1DDr3/G512wpnf21FBbucSpx5LCkIPbjzZNMXbpXgTVSlzLSeOMOe5Y2Sz6G0kd1B1zju0wtfocvUA4QUdygjLhnEBI6oleksgOPLOXVTYGhedTj+gAMu509upxSYE4ATVMuJ6QA8N4hXceqj9FRnhcw0XMVGweAA0JvbklZmOCGdgA3HMDkNxt1CGOyyWfW+XSuUO68t8S Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/25/26 14:07, Muhammad Usama Anjum wrote: > On 25/08/2026 11:36 am, David Hildenbrand (Arm) wrote: >> On 8/24/26 18:04, Muhammad Usama Anjum wrote: >>> Kernel nofault copy and string paths open-code page-fault disable and >>> enable around label-based loops, duplicating cleanup on success and >>> failure. >>> >>> Use a page-fault scope guard instead. Leaving the scope now re-enables >>> page faults on both paths without separate cleanup at the fault label. >>> >>> No functional change. >>> >>> Signed-off-by: Muhammad Usama Anjum >>> --- >>> mm/maccess.c | 53 +++++++++++++++++++++++++--------------------------- >>> 1 file changed, 25 insertions(+), 28 deletions(-) >>> >>> diff --git a/mm/maccess.c b/mm/maccess.c >>> index c59a0e092d24a..f695ceefe6fcc 100644 >>> --- a/mm/maccess.c >>> +++ b/mm/maccess.c >>> @@ -38,18 +38,17 @@ long copy_from_kernel_nofault(void *dst, const void *src, size_t size) >>> if (!size) >>> return 0; >>> >>> - pagefault_disable(); >>> - if (!(align & 7)) >>> - copy_from_kernel_nofault_loop(dst, src, size, u64, Efault); >>> - if (!(align & 3)) >>> - copy_from_kernel_nofault_loop(dst, src, size, u32, Efault); >>> - if (!(align & 1)) >>> - copy_from_kernel_nofault_loop(dst, src, size, u16, Efault); >>> - copy_from_kernel_nofault_loop(dst, src, size, u8, Efault); >>> - pagefault_enable(); >>> + scoped_guard(pagefault) { >>> + if (!(align & 7)) >>> + copy_from_kernel_nofault_loop(dst, src, size, u64, Efault); >>> + if (!(align & 3)) >>> + copy_from_kernel_nofault_loop(dst, src, size, u32, Efault); >>> + if (!(align & 1)) >>> + copy_from_kernel_nofault_loop(dst, src, size, u16, Efault); >>> + copy_from_kernel_nofault_loop(dst, src, size, u8, Efault); >>> + } >> >> While I understand what pagefault_disable+pagefault_enable does, it is >> completely unclear what scoped_guard(pagefault) does. >> >> Should this be scoped_guard(disabled_pagefaults) or sth like that? >> > > The `pagefault` guard is already defined in `include/linux/uaccess.h`: Ah, sorry, I thought this was added in this series. It's completely confusing. guard(pagefault)(); meaning "disable pagefault", what?! :) CCin Viktor: I see that the patch that introduced that has no acks from MM. I don't blame you, because the file is not actually listed under the MM section. I think this really needs to be cleaned up to clarify that we *disable* pagefaults. Usama, can you throw in a patch to clean that up? (calling it nofault, disable_pagefaults or whatever) -- Cheers, David