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 96A3338D419; Tue, 25 Aug 2026 10:36:52 +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=1787654213; cv=none; b=LwFYmBe2tKA6CcK6kB0AHOXssgTYpU0BJHqcG6MnuUby1/0vF45jmRPTgnFtj2lsgyDNA49VwbaO+TOpYxd4ac77efG3N55EG+CXNMaPFfCOEU2Yw8E9ngPVJU5F2oBLdqPpOZKNac6KNznF9uRA66TXVZNhTR+VzCaHyEAbMIQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787654213; c=relaxed/simple; bh=vKWQBCtWbAUaKRDldE3RKf0uL0I7yosrmqHU6mXlhXk=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=k30nDzj+X4Ot69N2MVDuqflH7EYJOwgr3ub44DmqnUmgWus2vFuiLKjPsVENbvhInuCAIUy5LFu/0OEN4URbSRHnFjHdq6fs+Ol0JLXsx50QZfwQzsbYptQ0Roi0i9B73m1knzqS/KViL56glxAYerESagleDRwEhzzAPRQvoS0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XTA/Mt2V; 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="XTA/Mt2V" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 540A51F000E9; Tue, 25 Aug 2026 10:36:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787654212; bh=MZb/JK/Dh5FAmjEvCkE963w53qfA4KfGbuSXikdZ8yc=; h=Date:Subject:To:References:From:In-Reply-To; b=XTA/Mt2VEn4QF+qKmJtNDTROxT68LJvWjnP/FbYThQypthq48pctFFdXh3GV54Iy2 QAagZKbHaKbxHp1ru2/7HYm8CmdGhcHddVnsHIEnfDFKRqKG/pl0X7hlgNszBrf5kW DWrmF3nWXeQxjURlRgjHtwB2MBeV+BOr4E35BdQewhRNecZsixOTJdW4y+dnnNmf2+ Hg7RWk3PIyW1uRtRpK6YXJnR0KCpbjL9KJkXwDQ+jY/G57QtoQLFQGfTZbD7cnqYDv NH60sP1sO7lC85HrF6Zg3u2bpnmLWxqN5vmQRkI5sJiQrFcF0LftR7kPUnK5K63jCU MUDBJJodTAdVQ== Message-ID: <79daa73b-0d34-4e84-8450-56f90bc700d4@kernel.org> Date: Tue, 25 Aug 2026 12:36:42 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 , 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" References: <20260824160523.3907021-1-usama.anjum@arm.com> <20260824160523.3907021-5-usama.anjum@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: <20260824160523.3907021-5-usama.anjum@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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? -- Cheers, David