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]) by smtp.lore.kernel.org (Postfix) with ESMTP id F03FDC02198 for ; Fri, 14 Feb 2025 21:18:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5167E280002; Fri, 14 Feb 2025 16:18:33 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 49F1D280001; Fri, 14 Feb 2025 16:18:33 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2CAC1280002; Fri, 14 Feb 2025 16:18:33 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 0AAED280001 for ; Fri, 14 Feb 2025 16:18:33 -0500 (EST) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id A76F180A10 for ; Fri, 14 Feb 2025 21:18:32 +0000 (UTC) X-FDA: 83119814064.23.1DA06A5 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf18.hostedemail.com (Postfix) with ESMTP id 4065F1C000A for ; Fri, 14 Feb 2025 21:18:30 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="K6/g8DxQ"; spf=pass (imf18.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1739567910; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to: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=pZ4WRQ+4bf26J6Ml4cW21FqlR1EOQRUQ0dnu91YpYUA=; b=iFoux0C2Rqa9iqYF0bteILM5bx6IPa9GaYCOmYkAKSPJh420aHPH711NerRW3dOL4TOEqQ 2cdMiko5Tw8NwVNVuHDfal9JCv1v4QOwNNWn/xhPhBsfy/dyNYVqQDhj06MLIW4qFWrukI ozf78GFvO55m46iWIXQxziwxFnOqdno= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="K6/g8DxQ"; spf=pass (imf18.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1739567910; a=rsa-sha256; cv=none; b=VvogL6O/dT4Nge/HWMKYMowy6CKpUXD+aEBtLQpzqrjCEk812csKH2l1kgIe01uNlQUeOu wOeKfHz3jvRJfxnqGVrHhmYCHhn33uTeBeLw5IB7djHwZwtEsxxNky2z1MU1JOVevs6GVx qN7IAWVY+7EuP+/LEWAVlh7ZOAYoWjo= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739567909; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=pZ4WRQ+4bf26J6Ml4cW21FqlR1EOQRUQ0dnu91YpYUA=; b=K6/g8DxQzLwstXQ3IjT22UubMnCrYq/r3Y0xmHDz4+p81YZBf418q9lhuLCRgqcvTCUiXm 8GAQntCVuiPaRcrmKSsTfseaDDT2WTS6LDBGGIkbJeJkzMehWSjnrAUi+uL94Fh+KOJ8wZ GlGBzja6oZi0e18/Rk0UXNkXGiDgiz8= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-119-ZcXHT_mWO9anqai3nVJAvw-1; Fri, 14 Feb 2025 16:18:27 -0500 X-MC-Unique: ZcXHT_mWO9anqai3nVJAvw-1 X-Mimecast-MFC-AGG-ID: ZcXHT_mWO9anqai3nVJAvw_1739567906 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-43945f32e2dso20328085e9.2 for ; Fri, 14 Feb 2025 13:18:26 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739567906; x=1740172706; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=pZ4WRQ+4bf26J6Ml4cW21FqlR1EOQRUQ0dnu91YpYUA=; b=JDJN7WGwW1wkf7JgZJaRA1WoXkmA0v5LTZ64ZnNKRO/QFfUdusz68+VAb9fClCtpJG /qixO7IChZ7rMaX8OxIYzTIPmGLPHHZcF2SA/9UXZMqCRBs14n6FHvWcdmC1a96RVPsc OHz8fPu0uMmdBrVhEUfdz7w2Uwu1pfVAwLohdD3+/+fU/6ng3IYhEQAaO8juuUPAkmuK dKctyPu2+WklWBPcKsYmj78DB+fDZXKW4V0jSCEsbVu0sDIAUc+Z2Afm5ujCR3nG/6NX ym0nf+Gs7So+YhfqDy+UCA5RcyXfBNTXWFmCPQPpjIK81+IVtzp4qb2EX+JJcIyd46M2 V2Mw== X-Forwarded-Encrypted: i=1; AJvYcCXA4vkXVYbayhZa0dICadHy/TV68ESqMca/LOsvEmB8n7MJzfr1GTgUlzSbj/hBPdbyBl5jg8Yi0g==@kvack.org X-Gm-Message-State: AOJu0YwjdGmQd7YemMo2Lh8pAEsoPqPtC0S1kWoZ+yRoxRVXy/WBZr0n S2KZxHubBMSctr7AP3cY2r/x1X3+SB3QhEEtnUf0EWHPXmhrsw9Impp2EUmFocJ3XvzmIpUm1hs 4/gsNmCLWMQvlkUWr1tR+yiEXuGM26jrcy7WamOpsnYjsyNAS X-Gm-Gg: ASbGnctGho4w+kEy4Kr0/r6ZURoz517f9WWc+Myykiqj7Pqn7C6gcfRgGSpUMhRkjhj KYLCJSszlg3IwcWF5mGEMRQnAh/2AahRNGLEs3FOO49yXrFaogh6IOxtG6JomptlxZ4+WK4XSs6 cq1rQuLl4b0lma0ru03ZMmSvmzc8kgyB9NVw2UVH3CqFH6JaKnijSDrjIC8EBUsFjPgxrUO2JuI CrNiShYF41KYhRW2EaumJ1buBd7YNujmmZUyLjfEWZKS+MVSizZghqj1xD8MB0hnX5G6ftMqNTT 0coWM0gOwk/k7vhCxJ+UBAeRaNeFoY1SCnaGRBRmaezu2OEVUMzzPHXd0clgGztuf4TQu+UuzQh ZPIkZIJ5YkM19CcqFEG9BLjWwA/Osw7So X-Received: by 2002:a05:6000:11d0:b0:38d:af14:cb1 with SMTP id ffacd0b85a97d-38f33f58dbdmr562471f8f.54.1739567906019; Fri, 14 Feb 2025 13:18:26 -0800 (PST) X-Google-Smtp-Source: AGHT+IH5kZWBu0PxIW4WyMNq/OR2r+EMBSRFuaSSqRdbBa7ZJG0Kg80XoUuFKY6KHDkv4z2UXa66pw== X-Received: by 2002:a05:6000:11d0:b0:38d:af14:cb1 with SMTP id ffacd0b85a97d-38f33f58dbdmr562457f8f.54.1739567905650; Fri, 14 Feb 2025 13:18:25 -0800 (PST) Received: from ?IPV6:2003:d8:2f22:1000:d72d:fd5f:4118:c70b? (p200300d82f221000d72dfd5f4118c70b.dip0.t-ipconnect.de. [2003:d8:2f22:1000:d72d:fd5f:4118:c70b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f258b41b5sm5664705f8f.14.2025.02.14.13.18.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Feb 2025 13:18:24 -0800 (PST) Message-ID: Date: Fri, 14 Feb 2025 22:18:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/3] mm: Create snapshot_page() To: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org References: <20250210212142.4002210-1-willy@infradead.org> <20250210212142.4002210-3-willy@infradead.org> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250210212142.4002210-3-willy@infradead.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ykQFDx2zi6Qs8Eismul6CF0P1sm4J5YcvJVoclSchW0_1739567906 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4065F1C000A X-Stat-Signature: bdbj3b6kd413tb7yopqs5fx5daw9zr5s X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1739567910-256909 X-HE-Meta: U2FsdGVkX1/vPFEsv+wsVuWSKPbp/ocTnvCdQkQy6X3w/mnFQ2Q5yZNxTpQ1ajaLspYk7WzbNsFnGm7fVFgaVTgvqnOIq88Q7AcZClIvUzKWEzj52NKrRmWtNhhOVQqCba6c6jnwpCoRE1PW3JxMmdjR7RC14YWTPWFl2zPaAf4M8tLyPSN8QTYc1MyJDy+V8LSSPo8pATL1iQ1FNgzwh33SjLWOKLDcvXbBeZyffsCrGB6RuPs6S5PUrPgIrF84jn39mkMxIRO6JkSF0neq+1clTdXdlEudehQUBJwjcvGtQnShQcGJLLvmoxt/XxXUxknz/pvyysgkGpjrFcXHNwZsflDFfAFg5lql6LkjekV/IbqNpi3fbSkbHB2xJ7N1MSiW0tyh8nryu5e/TKCzDpDHp9yZPgcGnW5VojjGhcMv+IHsD/6gjdtMcmr9SrOp952ukLrqGAKXE3IYpW+y3Mxf3oJCVncYQdNo+WOTy4LqSmwf7RaZjA0JJ2oMRkjvB7FySuLEXbMm+GR4BdJo8t3gy0svkFnr1wJ2NSE69RTM6pZ5Hcg2OxA0e9VbPwtngwoi+18PxpxtVj1XTLIKGIYvUSlHzTMFQ9aqatP3zhIRKSfXgzK220fJU65mdDBsH14IydHmNiyfz563sThJQtDNs/2DIlIiYOVIYJUuMctqacaD0tTreRZCPeu7X9UC7aTFgd8NfDOWC035BWh/4QhX4asfN4HuSQ4uv2aU8WHTYHkWfhvTJWAd5YXSjrAW/y3myx+wgse6xCuczf2QoCa7XeAwELa+ClgzYE5/gxcJOtMSyt2HWMH6vcohsm1zMgOatQBhVrpLh6gneCgycEQhm6vmfXO37R9vJPWAKgBDkf8jZ6sgu6MSuFFoC96oScyC753N+GYuam1qwzKuAorIeF7+b2J4lXLduQtaF1svG+rebyFIzED5x2/tH2XUurcjqUeCgsa1D6GmPt3 h/ZrpqcT 9AsAnCEnu1QtWduTU0f94uYwuP8h08Z9V34YEscF3Ry8jiEx4vajACJq5kdaITJnnVDOd9YF1E9U9os6f1ktZ0rRPd27TIwRqGpwct5Ua68KzemBvvn/p+0MbROWcDebJzIAU5w9vfgshSF1ixDHS5DjPWAFCvYXSMMRZGSt59oXCBoE/HHwnaDmLisPw5F9MBeEAuTm1e1ZMoKG+SUfyKGjf6fl/rYZej7cSgwyz33K938RVhgzXUKBdu7Q/jRLrV3uTpLJWbI2vJW2DHBdzQK2mB2e8+embrsgwdg2jx1N64aY76Negrno2nceJMQ0Cx2GysMgDar6OSVRT05Bk4ZDEzaXmPl4AJ4KGiOyD+uoBcd672O2H164D36gABXhj/645XI7HtE/hI3acFu0y9U+UbtxsDmNzrH8Kv9qrfCeMiSNdr49S6vZfkaxniURMBTAshhiJc8OS9GiSQBM/ULoTfL31CI/N+6ToTLi1dQ5PvkGkBTPpG2Rfxg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10.02.25 22:21, Matthew Wilcox (Oracle) wrote: > Move the guts of __dump_page() into a new function called > snapshot_page(). With that done, __dump_page() becomes trivial so > inline it into dump_page(). > > Signed-off-by: Matthew Wilcox (Oracle) > --- > mm/debug.c | 53 +++++++++------------------------------------------ > mm/internal.h | 2 ++ > mm/util.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 61 insertions(+), 44 deletions(-) > > diff --git a/mm/debug.c b/mm/debug.c > index fa3d9686034c..1ea5dacb1524 100644 > --- a/mm/debug.c > +++ b/mm/debug.c > @@ -120,54 +120,19 @@ static void __dump_folio(const struct folio *folio, struct page *page, > 2 * sizeof(struct page), false); > } > > -static void __dump_page(const struct page *page) > -{ > - struct folio *foliop, folio; > - struct page precise; > - unsigned long head; > - unsigned long pfn = page_to_pfn(page); > - unsigned long idx, nr_pages = 1; > - int loops = 5; > - > -again: > - memcpy(&precise, page, sizeof(*page)); > - head = precise.compound_head; > - if ((head & 1) == 0) { > - foliop = (struct folio *)&precise; > - idx = 0; > - if (!folio_test_large(foliop)) > - goto dump; > - foliop = (struct folio *)page; > - } else { > - foliop = (struct folio *)(head - 1); > - idx = folio_page_idx(foliop, page); > - } > - > - if (idx < MAX_FOLIO_NR_PAGES) { > - memcpy(&folio, foliop, 2 * sizeof(struct page)); > - nr_pages = folio_nr_pages(&folio); > - foliop = &folio; > - } > - > - if (idx > nr_pages) { > - if (loops-- > 0) > - goto again; > - pr_warn("page does not match folio\n"); > - precise.compound_head &= ~1UL; > - foliop = (struct folio *)&precise; > - idx = 0; > - } > - > -dump: > - __dump_folio(foliop, &precise, pfn, idx); > -} > - > void dump_page(const struct page *page, const char *reason) > { > + struct folio stack_folio; > + struct page stack_page; > + const struct folio *folio; > + unsigned long idx; > + > if (PagePoisoned(page)) > pr_warn("page:%p is uninitialized and poisoned", page); > - else > - __dump_page(page); > + else { > + folio = snapshot_page(&stack_folio, &stack_page, &idx, page); > + __dump_folio(folio, &stack_page, page_to_pfn(page), idx); > + } > if (reason) > pr_warn("page dumped because: %s\n", reason); > dump_page_owner(page); > diff --git a/mm/internal.h b/mm/internal.h > index 109ef30fee11..8fdfea104068 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -856,6 +856,8 @@ static inline bool free_area_empty(struct free_area *area, int migratetype) > > /* mm/util.c */ > struct anon_vma *folio_anon_vma(const struct folio *folio); > +const struct folio *snapshot_page(struct folio *foliop, struct page *precise, > + unsigned long *idxp, const struct page *unstable); > > #ifdef CONFIG_MMU > void unmap_mapping_folio(struct folio *folio); > diff --git a/mm/util.c b/mm/util.c > index 682ecdb1b1c2..9f9cf3933eb1 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -1239,3 +1239,53 @@ void flush_dcache_folio(struct folio *folio) > } > EXPORT_SYMBOL(flush_dcache_folio); > #endif > + > +/* > + * If you have an unstable reference to a page, use this to get a > + * somewhat-consistent (potentially outdated) snapshot. The consistency > + * is limited to the page being contained in the folio. You need to pass in > + * a scratch folio and scratch page, probably allocated on the stack. > + * You get back a pointer to the scratch folio you passed in, marked > + * as const to remind you not to modify this. > + */ > +const struct folio *snapshot_page(struct folio *foliop, struct page *precise, > + unsigned long *idxp, const struct page *unstable) > +{ A better interface might be something like: struct page_snapshot { struct folio folio_snapshot; struct page page_snapshot; /* page_to_pfn(page_snapshot) etc. don't work. */ unsigned long pfn; /* folio_page_idx(folio_snapshot, ...) etc. don't work. */ unsigned long idx; }; void snapshot_page(struct page_snapshot *ps, struct page *page); Or even (likely performance is less relevant) struct page_snapshot snapshot_page(struct page *page); __dump_folio() would then only accept that structure. In the future, we could indicate what kind of memdesc the page was a part of, and have "struct folio folio_snapshot;" be in a union with other types we support to snapshot etc.. -- Cheers, David / dhildenb