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 DD676C54E5D for ; Thu, 14 Mar 2024 16:23:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3354F800C0; Thu, 14 Mar 2024 12:23:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2E43F800B4; Thu, 14 Mar 2024 12:23:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 184BD800C0; Thu, 14 Mar 2024 12:23:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 0901F800B4 for ; Thu, 14 Mar 2024 12:23:04 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id BC79D1C186D for ; Thu, 14 Mar 2024 16:23:03 +0000 (UTC) X-FDA: 81896163846.26.24869D4 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf09.hostedemail.com (Postfix) with ESMTP id 9C1DD14001C for ; Thu, 14 Mar 2024 16:23:01 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="Gjtp4l2/"; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 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=1710433381; 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=9dTVRprwOc4uCCziuvhoGUV55JQxOFHbEAvnpbFO+EE=; b=IIcazd1GLWcYUGvjd3Xjk/KoW4rXQZvmy34FKJxD4TcZ8UTTcBzaDYcvHtJfbFtuEul50/ xYdFaFz3T1ZpKhIhMHaruVn4R785jrzr0q9CAiPl64Zi9bF3HnIw8Enqa8u9XyLTxzMEb3 gcR1E3WBQTEgEY/3xrzH3FyjlJIokB4= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="Gjtp4l2/"; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf09.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1710433381; a=rsa-sha256; cv=none; b=Cv9mVb9glXQzRUEUbI+SnHTwDwu76942KDjJmi8iH6Yjqfq0rSTljBLddJm/8RbVPBOHN1 On++XDrPqeOfoQW2Bel2rOABawLIxkIarzlTJ3Iv63Lr0HF6qj0jxvtzA+IphAb8JaOVsd 6MlSwEXdZ1AV+av05vq4fw4JjORE2Tw= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1710433381; 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=9dTVRprwOc4uCCziuvhoGUV55JQxOFHbEAvnpbFO+EE=; b=Gjtp4l2/MN6jTMg5xxtCt80yUzfRq98MTgU7yAY8zGkGmurfOC0120Pvyql7xcM/I1zYxO LZOlu/L+veJmPHbf5ZKI8hQn48XMl/kgSwSUk9qGPJQC8CxsnoOsfyGG6R4IaLhgoeTPeg z5mJcWt97wL2B32sSZLQ103x4kwPWgQ= Received: from mail-lf1-f70.google.com (mail-lf1-f70.google.com [209.85.167.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-131-em18rcBkPyyOwqAH36dkuQ-1; Thu, 14 Mar 2024 12:22:59 -0400 X-MC-Unique: em18rcBkPyyOwqAH36dkuQ-1 Received: by mail-lf1-f70.google.com with SMTP id 2adb3069b0e04-513b0d4e38eso1120300e87.0 for ; Thu, 14 Mar 2024 09:22:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1710433377; x=1711038177; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :references:cc:to:content-language:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=9dTVRprwOc4uCCziuvhoGUV55JQxOFHbEAvnpbFO+EE=; b=W8aAi+pStHUJryLGgRY79Dz24zzrbJidCwziJr60xCG/mI9cTyAaDJeVuOsviKRz3Z 2qwAqJMwCJjVOdkDMC4hjFk8LKZyiHZUShlGSKSr5tfuI0xOFxLUdvZPaGEygbmc8emI raQPBMXDA1jRStBQwXZ5xfdSieKPYqvs7DYcZiKyzna+nTiiD92WNHP0v0h3HSecxKCz Ww3qQM2KQ9T6MlNsf+9lX4JjwIZpgk3Twy8YiSC5BrgR1djTS1mH5xS7fMa3w/f0POzk LWFjn5Uw89YJ/7Ri4lDQFhHN3nx8vgz+Vn1YGXP7VwYCufnGRUKlXuZBdPwTdgz0X+hO /ytA== X-Gm-Message-State: AOJu0YxIiHbce70ESMRjP66uSLRDfTaIzjMnpYhYMhxyiU3EQunoCfdp ef3VX1GWJm7A5HbnAzPJDSB9l6Lb58nEt1Lfcbblgap8zUKh2b6gEqPpnZ24jejQms1Fks5uB03 aBF7tjU0snVYHhPDJUclX4pM/j73CH2GEu9B8bxfvQo6mrZjK X-Received: by 2002:a05:6512:52e:b0:513:84b6:6915 with SMTP id o14-20020a056512052e00b0051384b66915mr800512lfc.20.1710433377641; Thu, 14 Mar 2024 09:22:57 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEbCdL1y+45DM19tsdB3qqrAKWbNf0dtJKkCaJDgSwSLeykJgUlZD3NGmn5jIT/s5ZnC3cWiA== X-Received: by 2002:a05:6512:52e:b0:513:84b6:6915 with SMTP id o14-20020a056512052e00b0051384b66915mr800492lfc.20.1710433377210; Thu, 14 Mar 2024 09:22:57 -0700 (PDT) Received: from ?IPV6:2003:cb:c709:a00:7d7d:3665:5fe4:7127? (p200300cbc7090a007d7d36655fe47127.dip0.t-ipconnect.de. [2003:cb:c709:a00:7d7d:3665:5fe4:7127]) by smtp.gmail.com with ESMTPSA id u9-20020a05600c138900b00412f2136793sm6057908wmf.44.2024.03.14.09.22.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Mar 2024 09:22:56 -0700 (PDT) Message-ID: Date: Thu, 14 Mar 2024 17:22:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: updated documentation: Splitting pinned folios To: John Hubbard , Matthew Wilcox , Jane Chu Cc: linux-mm@kvack.org References: <57c9e228-9aca-4da6-a714-f175f053ff50@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: 7bit X-Rspamd-Queue-Id: 9C1DD14001C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: qtsx6p9qebfe5kdbij5k8segep364uo6 X-HE-Tag: 1710433381-197176 X-HE-Meta: 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 OwWC1lS0 PJeZt/RYhFWy+Tgxj2erMvoTpIO84kof9Hj/sdcCAZj+FDlFUfyZWPz9OfX25JQifNn/wvp/w8B8dp36fIjIg9I/qrmF9/tSk7fh6OIjSj4pOMVUv/y2yXeG2fhc8QqS5mewRPMi6NuHfhdzC281m4XS4cXfCO+MtRVxx 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 14.03.24 03:46, John Hubbard wrote: > On 3/13/24 2:20 AM, David Hildenbrand wrote: > ... >> The description is wrong. Whoever calls split_huge_page_to_list() must hold a folio reference. >> >> That folio reference will be transferred to @page (not the head page) once split. So @page can be used by the caller after the split succeeded. >> > > David and all, does this updated draft comment look accurate? > Note that in mm-unstable (maybe even mm-stable already), the function is now called split_huge_page_to_list_to_order(). > /* > * This function splits a huge page into normal pages. @page can point to any > * subpage of the huge page to split. The split operation does not change the > * position of @page. > * > * Prerequisites: > * > * 1) The caller must hold a reference on the @page's owning folio, also known as > * the huge page. > * > * 2) The huge page must be locked. > * > * 3) The folio must not be pinned. Pinned folios will not be split; instead, > * the caller will receive an -EBUSY. Maybe focus on unexpected folio references: 3) The folio must not be pinned. Any unexpected folio references, including GUP pins, will result in the folio not getting split; instead ... > * > * After splitting, the folio's refcount is transfered to @page (not the head s/transfered/transferred/ > * page, unless @page is actually the head page). The other subpages may be > * freed if they are not mapped. "folio's refcount" might be a bit misleading. It's more like "The caller's folio reference will be transferred to @page, resulting in a raised refcount of @page after this call ... " > * > * If @list is null, tail pages will be added to LRU list, otherwise, to @list. > * > * Both head page and tail pages will inherit mapping, flags, and so on from the > * hugepage. > * > * Returns 0 if the hugepage was split successfully. > * > * Returns -EBUSY if @page's folio is pinned, or if the anon_vma disappeared > * from under us. > */ > int split_huge_page_to_list(struct page *page, struct list_head *list) > -- Cheers, David / dhildenb