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 16E07C369DC for ; Wed, 30 Apr 2025 21:58:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 307A76B00B0; Wed, 30 Apr 2025 17:58:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2B5D26B00C1; Wed, 30 Apr 2025 17:58:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1305C6B00C3; Wed, 30 Apr 2025 17:58:21 -0400 (EDT) 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 E56D76B00B0 for ; Wed, 30 Apr 2025 17:58:20 -0400 (EDT) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id AC88CCAD4A for ; Wed, 30 Apr 2025 21:58:21 +0000 (UTC) X-FDA: 83392074402.18.68AC148 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf27.hostedemail.com (Postfix) with ESMTP id 21B2E40009 for ; Wed, 30 Apr 2025 21:58:18 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HoX5RiQG; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf27.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1746050299; a=rsa-sha256; cv=none; b=LuXtdJXK8kO3CZt+aneyKADBvKrfa34BkIrzYytdoxhUNbQYZoqlGAppjTa4qbcPekgKC+ d/gKTY8LtDqMc07MAvFTGN5780aS6yOwKa1qcv9MBkKuzYJPQTEpqGauQhAVPyd/2qFUhP WH6nfYATa4U2gD+wRf6iL+2FX4XOVqg= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HoX5RiQG; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf27.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1746050299; 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=ZAaCJDVeUqC/iRZsZzcfKKZg/z12nJeHt7AWXEHu+W8=; b=IfBkjWiKrAg9xDR2pn7DaxG05w1xtpmQGxSYO1WJpWk4NtGvVJ1TeUDYn4dXuKjZaWZSJP /KM1/0qLcpDfNRwtmkIBJt9dDnwEdBO2TTleTXP5qSdZxh/F0tCphI1VAu9puZXSuF/Btq LP8/YUZcVMKBGJQDuQKgylbCLx7faZg= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1746050298; 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=ZAaCJDVeUqC/iRZsZzcfKKZg/z12nJeHt7AWXEHu+W8=; b=HoX5RiQGLIidIw2Md4LUVntAS+IRVwQ14lphCL6SCDI3d0j6spTYADveqJHh9TLg+2n0tZ q6ZrSFdEnyLmF08P9ulidUf4VkqFFgZVjaODpSOQ9xyzhhzIaecaGFBsoaMQ4cv5+GMJ++ kHyJbjSjb0CDthtY5V0lHFibkQnHCAw= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-90-9KFCRe4nPFWlonQm9i9q1g-1; Wed, 30 Apr 2025 17:58:17 -0400 X-MC-Unique: 9KFCRe4nPFWlonQm9i9q1g-1 X-Mimecast-MFC-AGG-ID: 9KFCRe4nPFWlonQm9i9q1g_1746050296 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-3912fe32a30so89096f8f.1 for ; Wed, 30 Apr 2025 14:58:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1746050296; x=1746655096; 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=ZAaCJDVeUqC/iRZsZzcfKKZg/z12nJeHt7AWXEHu+W8=; b=RLdIKSdOxTBegUP+uhIZ0KcesEm3ZaM/sQ/Kvu5covCsB8e+KB+tGcDLFL58Xo8yE7 FRPoUOS748pPxmV3QGJyjKbJy5vESoPGAKrpebrLFyq6fBi2ooI6YT917QA8H/4HUOf6 WOeGUXyRBzlum5951hiiCxDpEdpZwJTP9eE7fuhTPior/dYEAzQjPjV4JBWzPrhQ1edz GtizdaLKZKGEBedbBp/rduyZfiZnVrLnnHZcSKuCVkbjCPcqrBOORgMPVx/MPA3hg46z KmnOaaemtSInt8WxpeuXWfdMUjciEdzDzPjAX/P9v2JgN2DPcPAVP/ni4KdO9sND27TB lhkA== X-Forwarded-Encrypted: i=1; AJvYcCU9i8+q2CqChc6sDS3uutKb546IWtqBx9uKPRLSssZyvCHFnQddwM3mSK8eb5a3tnEQoJJ/YXOz7A==@kvack.org X-Gm-Message-State: AOJu0YyfiUmDW9LDJ8kHmKrxD1hvGAh9EBCh48uqDYzwRC2sTZosq6lK PBphKweg7Zm91oNhESCAZ+UDEFahLfrrcOjrBHAHpe+FMUo/aTBnwbXExUZvovLIcEm7BPEoGwD SjROH4G3gjlAUwOZyryzXuD2GNUad7LIIlln3Srt3H3FQgzk+ X-Gm-Gg: ASbGnct332EJGj+JLV0YOhyVJUAJzaYCQX2PjSAZkS7irbNX/RR8NvaL2qq+5y+DwkN +HQvScZ+CcSiOuT01bAIl0aOLcHjwCIU1mhqW6ygLdHuDHcSi0EO6v+mhC27qU8pLRGaxAcKS8U OKnSsM9dhN2TXZQTTP+FFgVnps9quCSYZ5o1WFR56wGESp7hFoFn+6lGvcbApcm45wpnf04zCWy xLq1pEv7TejaTUMOArQS0XukmcWv4yrLt1+/QyritWXcEQjaAQfF2FcA7THeBDWYB3wrMhAX3v0 04vO1P9pybsXdoKyTAC+7Cwt47CJRwAG0I5PJseHZA== X-Received: by 2002:a5d:64a5:0:b0:39f:efb:c2f6 with SMTP id ffacd0b85a97d-3a094053655mr72090f8f.33.1746050296025; Wed, 30 Apr 2025 14:58:16 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHIUfs9wV073mQDXRyQLoTF/v/RVuHpOr0Qx8MhdARsvRHVgQY3znuEKqA1Jf53XmKmX6ViRw== X-Received: by 2002:a5d:64a5:0:b0:39f:efb:c2f6 with SMTP id ffacd0b85a97d-3a094053655mr72076f8f.33.1746050295698; Wed, 30 Apr 2025 14:58:15 -0700 (PDT) Received: from [192.168.3.141] (p4ff231f0.dip0.t-ipconnect.de. [79.242.49.240]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a073e5d264sm18470464f8f.95.2025.04.30.14.58.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Apr 2025 14:58:15 -0700 (PDT) Message-ID: <7ab1743b-8826-44e8-ac11-283731ef51e1@redhat.com> Date: Wed, 30 Apr 2025 23:58:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/3] mm: introduce new .mmap_proto() f_op callback To: Lorenzo Stoakes , Andrew Morton Cc: "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Jann Horn , Pedro Falcato , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Viro , Christian Brauner , Jan Kara , Suren Baghdasaryan , Michal Hocko References: 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-MFC-PROC-ID: GxaRxMa7VDvDEsRMmNHWc_afNmW26RwrtkE81U-NMZs_1746050296 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 21B2E40009 X-Stat-Signature: n3hdmd95erpk3zquebgx4anknz7stbu3 X-Rspam-User: X-HE-Tag: 1746050298-284015 X-HE-Meta: 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 1dygyOdp 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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 30.04.25 21:54, Lorenzo Stoakes wrote: > Provide a means by which drivers can specify which fields of those > permitted to be changed should be altered to prior to mmap()'ing a > range (which may either result from a merge or from mapping an entirely new > VMA). > > Doing so is substantially safer than the existing .mmap() calback which > provides unrestricted access to the part-constructed VMA and permits > drivers and file systems to do 'creative' things which makes it hard to > reason about the state of the VMA after the function returns. > > The existing .mmap() callback's freedom has caused a great deal of issues, > especially in error handling, as unwinding the mmap() state has proven to > be non-trivial and caused significant issues in the past, for instance > those addressed in commit 5de195060b2e ("mm: resolve faulty mmap_region() > error path behaviour"). > > It also necessitates a second attempt at merge once the .mmap() callback > has completed, which has caused issues in the past, is awkward, adds > overhead and is difficult to reason about. > > The .mmap_proto() callback eliminates this requirement, as we can update > fields prior to even attempting the first merge. It is safer, as we heavily > restrict what can actually be modified, and being invoked very early in the > mmap() process, error handling can be performed safely with very little > unwinding of state required. > > Update vma userland test stubs to account for changes. > > Signed-off-by: Lorenzo Stoakes I really don't like the "proto" terminology. :) [yes, David and his naming :P ] No, the problem is that it is fairly unintuitive what is happening here. Coming from a different direction, the callback is trigger after __mmap_prepare() ... could we call it "->mmap_prepare" or something like that? (mmap_setup, whatever) Maybe mmap_setup and vma_setup_param? Just a thought ... In general (although it's late in Germany), it does sound like an interesting approach. How feasiable is it to remove ->mmap in the long run, and would we maybe need other callbacks to make that possible? -- Cheers, David / dhildenb