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 4E37CC3ABAC for ; Tue, 6 May 2025 14:34:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5F8986B0096; Tue, 6 May 2025 10:34:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5A8E96B0098; Tue, 6 May 2025 10:34:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4223E6B0099; Tue, 6 May 2025 10:34:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 22F9D6B0096 for ; Tue, 6 May 2025 10:34:11 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 062E1C02DD for ; Tue, 6 May 2025 14:34:12 +0000 (UTC) X-FDA: 83412727944.25.7F06F3E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf13.hostedemail.com (Postfix) with ESMTP id 831C020018 for ; Tue, 6 May 2025 14:34:09 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hOzcdHdw; spf=pass (imf13.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1746542049; 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=zSYTzLzA4I8JDg4pBsPS0ZO1xAUoaORmUFU9cepMeAE=; b=ROjB5VkU7XP22AB6mV9sUHGkVj+kYfxU+cO+GuCayCQkaDlFr7YCk9parCU3RECELHqame m6dCaIJITmhKqPsb1K07LN8oMGJus4TO+DCJatTYH4GAt77d41H9YVzdaDJH15Yuw/X3eZ dQVabDIFOi2IsZ0GmWeStuTROIhl/Dw= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hOzcdHdw; spf=pass (imf13.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1746542049; a=rsa-sha256; cv=none; b=ypHIkybuXFd5TY1gJMtT44QX9mqb99ZwzMaH32u2xa9GzRkXE8rDfXC00Ff0voPWsPj5CI 9lvIX6rZqQfsvYk4cWGeY0eFivp2PR8I67d3ccWV8nN6CVwHWGBRoKiSYLzK7sxgjbuib8 Sy8qkuyt+9uiDaMam8q0P9r5FIKDF1s= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1746542049; h=from:from: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:autocrypt:autocrypt; bh=zSYTzLzA4I8JDg4pBsPS0ZO1xAUoaORmUFU9cepMeAE=; b=hOzcdHdwy04cs3sz8TsWmSI+FY4OSlDixbcO72INzXDSfCOTNdttpHyTDQyBTDdFMF5e0K ASx4RyBzP8H7DIYE0s3VC+8bKGQQ8yKx8dDuLx2szEWiHiDaMXYspojC4L9IKmgSsSE4l6 jgKnklbyWJ72Z+xA14dQ73Py20upoeg= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-269-5Tw5wNEQMvKHBtkTW2IzRw-1; Tue, 06 May 2025 10:34:07 -0400 X-MC-Unique: 5Tw5wNEQMvKHBtkTW2IzRw-1 X-Mimecast-MFC-AGG-ID: 5Tw5wNEQMvKHBtkTW2IzRw_1746542046 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-3912d5f6689so2748194f8f.1 for ; Tue, 06 May 2025 07:34:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1746542046; x=1747146846; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=zSYTzLzA4I8JDg4pBsPS0ZO1xAUoaORmUFU9cepMeAE=; b=F0Byr+EYvN9J/rFrBpU6GZ/aS1twP8iYrNzcC7EAHaQZDK+Lp8J3cNC5iRvEZP4V5c JEWDLxoxD1AjA65X99xrDy4h1k0Q+0hIQx8Jx85IpTzh1DcsjWwcktRZTcqWzyg3XzCK U4zbwpx6B2+rqeCxiznfSmqfwnlNOEiRdQ6oiKmSRp4I+v2fbAMduBLdfiJSQxO5416O XLUMhrYTb41j/vHBNtovsUAKg6rWGWedZkoAfnnX5dwjIIyTauWEItKXZpABFZQqM21q GB+GxIXGsNsTBqs2ofKST2eZt7a7A8SRJdidMm8fPSA2tUFpDszqA+/H5GcwvcvZHFJH 8DDw== X-Forwarded-Encrypted: i=1; AJvYcCWIeBH+XSb77tXsQKNmIGtI1OYNAhmqvfeXNgyK2Zk7ymnl8s/uG8/8x1Iw5O1LxZ6iLq8bKTwslQ==@kvack.org X-Gm-Message-State: AOJu0YxQO4L+ySs2K+EL+DEr+QspglSveK+0p41vqpsYpGFVZtSPKk7a /aas9zaAXHXiHT1z0+RR5OkmU9QNRJzvehR82WEsFUJoD/2J/V2PvzuHytaGVSUb1E7ACNYCOeJ p7AQQfNRow+5NBG7qgioHWZQ/sGIpGSKjKDCkU6e2gdyFgeoh X-Gm-Gg: ASbGncvOMtJqcMXxzQzlCR031bE6irIqz+KRBZYGG4gOF4JtG4qpV3v/bvDpg50/mcD Q8J5Xusq/2+MucK5IFW7PTKFtV6VlOMiNyfYaGdtUeWrtge4wumXYnt3POAbZayj9oSTlo97f5K JAEzu1ZGI62GrKF/ZarmKx40UczzTX0mLOEBP3r3wNhRqYocDULfcTtJHJ7od8KsJejTVaAzfPe UVB7XYbJIn3PWfdo6ZBfPcpp3pzkunZSwyxIAbGQP16ZRGkm11I7v1t4KadJWLW2z1JHtWiTUC9 0f5PXYzoDVsQYcPupz8kPmgidemaBCnDt6gsG6/hbzL1CuzpVRg= X-Received: by 2002:a05:6000:2204:b0:39c:268e:ae04 with SMTP id ffacd0b85a97d-3a09fd0d09dmr8962661f8f.0.1746542046348; Tue, 06 May 2025 07:34:06 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFUJh5j9TVIQWsrv8+lQopvkfyv6q0sW1QF6jcjHqVsYskzyqmZ/uFzWwuXJfP4bPKTDBUOGA== X-Received: by 2002:a05:6000:2204:b0:39c:268e:ae04 with SMTP id ffacd0b85a97d-3a09fd0d09dmr8962630f8f.0.1746542045945; Tue, 06 May 2025 07:34:05 -0700 (PDT) Received: from ?IPV6:2a01:599:915:8911:b13f:d972:e237:7fe2? ([2a01:599:915:8911:b13f:d972:e237:7fe2]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-441b8a286b9sm170753685e9.28.2025.05.06.07.34.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 May 2025 07:34:05 -0700 (PDT) Message-ID: Date: Tue, 6 May 2025 16:34:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 6/7] mm: Batch around can_change_pte_writable() To: Dev Jain , akpm@linux-foundation.org Cc: ryan.roberts@arm.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, anshuman.khandual@arm.com, peterx@redhat.com, joey.gouly@arm.com, ioworker0@gmail.com, baohua@kernel.org, kevin.brodsky@arm.com, quic_zhenhuah@quicinc.com, christophe.leroy@csgroup.eu, yangyicong@hisilicon.com, linux-arm-kernel@lists.infradead.org, namit@vmware.com, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com References: <20250429052336.18912-1-dev.jain@arm.com> <20250429052336.18912-7-dev.jain@arm.com> <25dcf969-e479-4d4a-a95c-0e83706af99e@redhat.com> <9a770aec-a020-4199-a53e-eddda657999d@redhat.com> <0857761c-bb4c-4ea5-a96a-90d555673527@arm.com> 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: <0857761c-bb4c-4ea5-a96a-90d555673527@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: vpAkie-XYZ5d9yVwB7m0Yq7sdQhBJ80Uqhqrw172q-4_1746542046 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 831C020018 X-Stat-Signature: kk79gidkn3inqee78w64xfc5fm56bw7g X-HE-Tag: 1746542049-497242 X-HE-Meta: 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 0UklVaoh H6KHXJ+eujDxOND7hkeQ4I7hIDGm9Jyjn92o+hXCxZ1BHJvHjoY7U1HAFODRZtUrb6/4eafKnb3tpNgxsmk3xrIoW9VeaF7g22wwUzMuzYUKTE822eLkWrivTZoxIycg5l2X3QDk/Jk6zQCJE1PK0CDlspzRkH2qMOEj1RSNC2WPEV8GIOOktJWNP6rG5+VUs+TLMKzPI0389vTz0hXWUpEP+zTWexDAvlhmyJThaZRh2bieqxJvC9zlb5zcL0uMzaz3Oco77E8Dz07ts3jpb2D/VdkPlLJte4TaHkRH0UmCkIsEw7gDG+NQVldvPm0fXRekr/bUZLTcaj33W+bU9wUjWpsY0vBeFKokOhKGhkVKIa4X/QD67OFgNSgjoTl7bwBm5iF0r2p7YNx+jmyxNpB6ZHLHbsajGmRSSLTzre1FuAKWC9URyXIrDxqeHZ8Ko2ttJRK7SDCm6Ln61coW6jws8L8nqP8rv6eEbjbck1r1SmJ5+K63+PtIZ4esNxUEq//Fs36zSfn90zn992gR9PFK6sznlqo5WEGlq 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 06.05.25 11:16, Dev Jain wrote: > > > On 29/04/25 2:57 pm, David Hildenbrand wrote: >> On 29.04.25 11:19, David Hildenbrand wrote: >>> >>>>    #include "internal.h" >>>> -bool can_change_pte_writable(struct vm_area_struct *vma, unsigned >>>> long addr, >>>> -                 pte_t pte) >>>> +bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned >>>> long addr, >>>> +                  pte_t pte, struct folio *folio, unsigned int nr) >>>>    { >>>>        struct page *page; >>>> @@ -67,8 +67,9 @@ bool can_change_pte_writable(struct vm_area_struct >>>> *vma, unsigned long addr, >>>>             * write-fault handler similarly would map them writable >>>> without >>>>             * any additional checks while holding the PT lock. >>>>             */ >>>> -        page = vm_normal_page(vma, addr, pte); >>>> -        return page && PageAnon(page) && PageAnonExclusive(page); >>>> +        if (!folio) >>>> +            folio = vm_normal_folio(vma, addr, pte); >>>> +        return folio_test_anon(folio) && ! >>>> folio_maybe_mapped_shared(folio); >>> >>> Oh no, now I spot it. That is horribly wrong. >>> >>> Please understand first what you are doing. >> >> Also, would expect that the cow.c selftest would catch that: >> >> "vmsplice() + unmap in child with mprotect() optimization" >> >> After fork() we have a R/O PTE in the parent. Our child then uses >> vmsplice() and unmaps the R/O PTE, meaning it is only left mapped by the >> parent. >> >> ret = mprotect(mem, size, PROT_READ); >> ret |= mprotect(mem, size, PROT_READ|PROT_WRITE); >> >> should turn the PTE writable, although it shouldn't. >> >> If that test case does not detect the issue you're introducing, we >> should look into adding a test case that detects it. >> > > Hi David, I am afraid I don't understand my mistake :( PageAnon(page) > boils down to folio_test_anon(folio). Next we want to determine whether > the page underlying a PTE is mapped exclusively or not. No. :) There is your mistake. We need to know if this folio page is *exclusive* not if the folio is *mapped exclusively*. I know, it's confusing, but that's an important distinction. You really have to test all PAE bits. I recently sent a mail on how we could remove PAE and encode it in the PTE value itself (W || (!W +dirty)), which would mean that we could batch more easily. For the time being, we have to stick with what we have. -- Cheers, David / dhildenb