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 C54E4C3DA4A for ; Thu, 22 Aug 2024 12:19:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 544626B00FB; Thu, 22 Aug 2024 08:19:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4F1E76B01FA; Thu, 22 Aug 2024 08:19:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2D14C6B0112; Thu, 22 Aug 2024 08:19:10 -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 0650A6B01FA for ; Thu, 22 Aug 2024 08:19:10 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 97D04A8836 for ; Thu, 22 Aug 2024 12:19:09 +0000 (UTC) X-FDA: 82479786018.23.3922A1D Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf15.hostedemail.com (Postfix) with ESMTP id 47ED5A001A for ; Thu, 22 Aug 2024 12:19:07 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hWyZfSpB; spf=pass (imf15.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=1724329083; 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=TkmBKasCieEXjo2TVqkYnfAxfMqsNMhdyVXpm9rsAmM=; b=ebZwSkmK8wpIbT3LeC8ajUyrOGd3PkWwDz0SkXivXF3vBeCGDXh5wi38e3EDJ9bE4v98Fx YvOS5OJ4/Ato+k69QNr+dPSs8khqYxpn3R06qw7Wc5qHC1rNzR5gXTwfN9HEFIEIn7naOU /e24MxSKTi1S2TRYacaMiHRXTQAaHrI= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hWyZfSpB; spf=pass (imf15.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=1724329083; a=rsa-sha256; cv=none; b=IbNvG7tl/L6+dwt0A9sxo57CjsajMbZmAdYJ9S5QKQAMSZErGpBvNWuEW7V44QOE2Y/tko vOhUgwrhfz8+DOK5J8hMYHGdGZ+unVdFrFcCNj0INeHp+jYFv5ZEkwrMn9a8PBo3PueTIo cgrvmIwyVdo0MkHYBGV1rRWRQEs9JeY= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1724329146; 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=TkmBKasCieEXjo2TVqkYnfAxfMqsNMhdyVXpm9rsAmM=; b=hWyZfSpBzNBhtjd/zKEhWjmTvdMaYnL20AWuKNVraFdJRDekZQdr8oUfLTjWazw8Je3ywE rtkEKWYP27rOqpyseqqzhHDdBLWJteAoVlpLpCUhJ7IPENfAlfJIH5TTQWBO5kesNxmTkO AHdts5dTdqyc5b2z9Kn5QnSWBtDGD7E= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-93-XhKO0osVN5aN7zJS_Cd7BQ-1; Thu, 22 Aug 2024 08:19:05 -0400 X-MC-Unique: XhKO0osVN5aN7zJS_Cd7BQ-1 Received: by mail-wr1-f71.google.com with SMTP id ffacd0b85a97d-3719559c51dso370107f8f.2 for ; Thu, 22 Aug 2024 05:19:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1724329144; x=1724933944; 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=TkmBKasCieEXjo2TVqkYnfAxfMqsNMhdyVXpm9rsAmM=; b=huvgoiTMwQNmE76IhMsiRNxPEozZ2+GZDY6RZ0oZ8QEh1rGakSMsC+rHfe2NBdXEfX QlKy3AFEkqy3rAfSK8HP0YXzmO/q+ezS2dnfBYwmpw7lo15DwrBRB9cvb7v8BG5cvXSH waQ2TVZesmniBmSDKoF8CTvMM1PtJuyjNgEVVVpSskibLHwAjhY0AiKTvIQT5QYELEnv pJIeQP04gHtEdnZdsPNsRZMZQvLaaAitpZMdt/jnyi/ciF9l7s6ptI+Qn1j4QxBcVdSp mvVEtZeGIMEJplJ13tP9L1AMf4LvoWG2UvaQAx2ue7VQnTso6lL5igKp10kMMr933yFw IyjQ== X-Forwarded-Encrypted: i=1; AJvYcCVW51jEhlNT/LSFPULZByZifDfgPkxBC86xoiAPyOwknDN6lUGkWEdDVKHuXqIxAA5/kGVLgVRHiQ==@kvack.org X-Gm-Message-State: AOJu0YwzzwXtzEAfzWs09U/3KCAZdwUtTyAyiQFr1ZdL6F/wOZb9R2nH XybG3dFSi3qxYRjmsSB6qUfPlDJK5IK++nKdHkRf6bafFbGjzusnYT+YJflNZIAe2HPMdWkiexH Ts+rGi6CEHjpMISeKREcCxV7ccGfMVaitg8/E+T1D50ZaZK3N X-Received: by 2002:adf:f60d:0:b0:367:9621:6fa with SMTP id ffacd0b85a97d-372fd5ca8damr3645439f8f.37.1724329143943; Thu, 22 Aug 2024 05:19:03 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEUx+YDDxgqRcDJR/2ELwCGRMB9JIiGMlHuOPJmREuQ076olN3nXdv+XbVkjm1FNBbf+TOJ2g== X-Received: by 2002:adf:f60d:0:b0:367:9621:6fa with SMTP id ffacd0b85a97d-372fd5ca8damr3645400f8f.37.1724329142983; Thu, 22 Aug 2024 05:19:02 -0700 (PDT) Received: from ?IPV6:2003:cb:c70f:2b00:f928:47d8:c9be:9d87? (p200300cbc70f2b00f92847d8c9be9d87.dip0.t-ipconnect.de. [2003:cb:c70f:2b00:f928:47d8:c9be:9d87]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42ac515a2a5sm23144385e9.20.2024.08.22.05.19.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Aug 2024 05:19:02 -0700 (PDT) Message-ID: <38d6caeb-1aba-43d2-8daf-12b9aaba77bd@redhat.com> Date: Thu, 22 Aug 2024 14:19:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 06/14] mm: handle_pte_fault() use pte_offset_map_maywrite_nolock() To: Qi Zheng Cc: LEROY Christophe , "hughd@google.com" , "willy@infradead.org" , "muchun.song@linux.dev" , "vbabka@kernel.org" , "akpm@linux-foundation.org" , "rppt@kernel.org" , "vishal.moola@gmail.com" , "peterx@redhat.com" , "ryan.roberts@arm.com" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-arm-kernel@lists.infradead.org" , "linuxppc-dev@lists.ozlabs.org" References: <239432a0bc56464e58a6baf3622fdc72526c8d57.1724226076.git.zhengqi.arch@bytedance.com> <6a586524-5116-4eaf-b4f3-c1aea290d7c1@cs-soprasteria.com> <4b867535-8481-4fa1-bed1-ad25a76682f0@redhat.com> <61c05197-0baa-4680-ad24-5965ba37dc35@redhat.com> <83142dc8-edcf-4e47-8215-8b359a2b7156@bytedance.com> <04dccff9-87dd-4e97-a712-b62fa51b32f7@redhat.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: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: kt4kw5pm1wy5xsbap5esdzakooyqwyga X-Rspam-User: X-Rspamd-Queue-Id: 47ED5A001A X-Rspamd-Server: rspam02 X-HE-Tag: 1724329147-659147 X-HE-Meta: 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 1yZENWLq 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 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 22.08.24 14:17, Qi Zheng wrote: > Hi David, > > On 2024/8/22 17:29, David Hildenbrand wrote: >> On 21.08.24 12:03, Qi Zheng wrote: >>> >>> > > [...] > >>>>>>>>> -        vmf->pte = pte_offset_map_nolock(vmf->vma->vm_mm, >>>>>>>>> vmf->pmd, >>>>>>>>> -                         vmf->address, &vmf->ptl); >>>>>>>>> +        vmf->pte = pte_offset_map_maywrite_nolock(vmf->vma->vm_mm, >>>>>>>>> +                              vmf->pmd, vmf->address, >>>>>>>>> +                              NULL, &vmf->ptl); >>>>>> >>>>>> I think we discussed that passing NULL should be forbidden for that >>>>>> function. >>>>> >>>>> Yes, but for some maywrite case, there is no need to get pmdval to >>>>> do pmd_same() check. So I passed NULL and added a comment to >>>>> explain this. >>>> >>>> I wonder if it's better to pass a dummy variable instead. One has to >>>> think harder why that is required compared to blindly passing "NULL" :) >>> >>> You are afraid that subsequent caller will abuse this function, right? >> >> Yes! "oh, I don't need a pmdval, why would I? let's just pass NULL, >> easy" :) >> >>> My initial concern was that this would add a useless local vaiable, but >>> perhaps that is not a big deal. >> >> How many of these "special" instances do we have? > > We have 5 such special instances. > >> >>> >>> Both are fine for me. ;) >> >> Also no strong opinion, but having to pass a variable makes you think >> what you are supposed to do with it and why it is not optional. > > Yeah, I added 'BUG_ON(!pmdvalp);' in pte_offset_map_ro_nolock(), and > have updated the v2 version [1]. No BUG_ON please :) VM_WARN_ON_ONCE() is good enough. -- Cheers, David / dhildenb