From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 02CB7202F79 for ; Tue, 1 Jul 2025 08:34:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751358882; cv=none; b=teSYr37Y1Wkf1BQqO18rg/8INwA/ut7vB0pg36n8ovzTs9B9Ec/UWlLdFqb3mHku+Ery85QPwPfrjadDdSv0QvtAEWgn8ewHIos3zqAJGFUA83U40Lrj9dZqvzfhwQxLf1l4hpRmgImjRftmKiBDZGjHu9Eq1twSQrBGm62DEg8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751358882; c=relaxed/simple; bh=lbS24cMJ3Oc3OQhNt/DSzGyRJOx2dd6GD9LmhgcNCIw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ir1AlOf1Bi9UwVtVOnrpLtS9fU9jg+JBmLAkzJ+cVurMbq8tZqE1WuiC4fhmqESZtLlJ13eZBjwK5LVNo6nRUt6BXf8U1T74JOIFyJYhXWBojtLVCH5MC07JTsVYyOStW1tVfDlwcQ0V94WwVqKpqTi+KFnNKj5VB72PmjcyZdQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=IauvyTpU; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="IauvyTpU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1751358879; 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=XqmCuun4O9S0uzldpDEz2Hy5OKYqaKQE+fhycCpdDZQ=; b=IauvyTpUQGz4y7u6G2EFQE2MK7qnnJF0DYfygEVRN6X0JpzUO4kPAe93L2NFT1uJgYRtOr 5wqJ4z0UOp0LDLKgqYSmYpYQ6HFQcyM4oaAKNqXU36kdVz1S/OwjwdSsTIpyxP7KyZf88g qpEPWlyek5KUbeFy53Wc2fmJBUcf/IE= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-615-E9aQtTlJN2u-mZyJxCl1bg-1; Tue, 01 Jul 2025 04:34:38 -0400 X-MC-Unique: E9aQtTlJN2u-mZyJxCl1bg-1 X-Mimecast-MFC-AGG-ID: E9aQtTlJN2u-mZyJxCl1bg_1751358877 Received: by mail-wr1-f69.google.com with SMTP id ffacd0b85a97d-3a4edf5bb4dso3533875f8f.0 for ; Tue, 01 Jul 2025 01:34:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751358877; x=1751963677; 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=XqmCuun4O9S0uzldpDEz2Hy5OKYqaKQE+fhycCpdDZQ=; b=Wvnr5/h4tGnEAzVTK7t638eaTNTx0eHxePdetQ4tuSHpvd+o2ZU2+OcCy06Kq/B6Ak vnA+qe+aXApLVNm8t10h8k9qI4d4zlTpWdVTXcoTSoVjAZfZiaTW/l3t6GtMCArntkRX EIIPg6cmd4PqZIxA9ddmtKb/TAlnOUMPivgjr8GZWigtnZeWf31F3SHnjAYnQXgG/wLD EOtI1iCnhHJHZ8/6t+O3k/X1GjjlqGI6DheHZeFhO7pbT8s/6IHQSala6gwveG3ejyhW bDQDGrYs8x4SfL5UIG9F9XAcuOLwUY4FRYLpY1cVepYgZz/t5cCRlujkbxQdYdrn2NPQ NtWQ== X-Forwarded-Encrypted: i=1; AJvYcCWL2sQg7bXTrKueardnyuOfzh2OD/ekCdqAn6HcXfMlcqIYUix3OyB7eGpYrBtKaimIlLFC2wYpE2C0H3hW@vger.kernel.org X-Gm-Message-State: AOJu0Yzw2OgCJEZwPUxUkp/OvSaLWMgxBql0wtImUAQ1/YLmm1Z2nEPC 8mEHLxq9Ac3OhU227btQ3kPDcvTpCf5rh+2ZyP5DIl0ro7XANIEne50yJ5+Sh9IBb3K0yYZ0s7A hCqKS1vRJ3paD7QcEq/RUE5EcTwnYc1njeRp9b0Xr1lPCaTm1U7syAXCREwGUO7oSm0c= X-Gm-Gg: ASbGncvL+o8lSkArWQ9+zIGcrt8fYl4sfQDkcRGTyvHqgRb2duQY7MNFpx2LWIIH7dF /xMIwu/BY3YWlh6NJFU5tQxVZnJdXSrGHkjMO0xyhvI+uX3ls1+SPqLKIT8t9sfpZsltXenEjOm vtctuWtBMciuw8uVDYXIqV2i6IaGfagPX7lLob72c5RiT3VZvQHHB53XhV0CmKiAim8d612/Vj4 cZDTbmzAP1erlVP2Ag8paFIb1es4XVgUc8hPgDecuuwTQr6/WKslRdzvHLxN/qD2oq1hV+TrQ4i 0UPTDZCdCImxQMEnK56jj8GpaS1kWqd7nEAjPIzhbXMCjZKKKOYNeDjrfsjc70w5pnXSgui6eoQ yjxhfgVdgEZhP+6C4OgI50Rdf2DFnl8z0eSs6JOv5ZqPo5wCy3g== X-Received: by 2002:a5d:60c4:0:b0:3a4:d898:3e2d with SMTP id ffacd0b85a97d-3a90d69c269mr11346914f8f.24.1751358877359; Tue, 01 Jul 2025 01:34:37 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEF8cObrwLhR7FvJoCAh0zan/cCbAjnhUquLcc9ptC1Omlee0lmAh8jtPfZiWWwygYZe4cdqg== X-Received: by 2002:a5d:60c4:0:b0:3a4:d898:3e2d with SMTP id ffacd0b85a97d-3a90d69c269mr11346880f8f.24.1751358876846; Tue, 01 Jul 2025 01:34:36 -0700 (PDT) Received: from ?IPV6:2003:d8:2f18:7500:202e:b0f1:76d6:f9af? (p200300d82f187500202eb0f176d6f9af.dip0.t-ipconnect.de. [2003:d8:2f18:7500:202e:b0f1:76d6:f9af]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a892e5f943sm12511942f8f.101.2025.07.01.01.34.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Jul 2025 01:34:35 -0700 (PDT) Message-ID: <84e1eeeb-c78f-4735-a6d2-4bb15ea1fbce@redhat.com> Date: Tue, 1 Jul 2025 10:34:33 +0200 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 04/29] mm/page_alloc: let page freeing clear any set page type To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org, Andrew Morton , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Jerrin Shaji George , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Alexander Viro , Christian Brauner , Jan Kara , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Minchan Kim , Sergey Senozhatsky , Brendan Jackman , Johannes Weiner , Jason Gunthorpe , John Hubbard , Peter Xu , Xu Xin , Chengming Zhou , Miaohe Lin , Naoya Horiguchi , Oscar Salvador , Rik van Riel , Harry Yoo , Qi Zheng , Shakeel Butt References: <20250630130011.330477-1-david@redhat.com> <20250630130011.330477-5-david@redhat.com> <8c5392d6-372c-4d5d-8446-6af48fba4548@lucifer.local> <06e260cf-9b63-4d7c-809c-a9f2cda58939@lucifer.local> From: David Hildenbrand Content-Language: en-US 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: <06e260cf-9b63-4d7c-809c-a9f2cda58939@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01.07.25 10:27, Lorenzo Stoakes wrote: > On Tue, Jul 01, 2025 at 10:17:13AM +0200, David Hildenbrand wrote: >> On 30.06.25 17:27, Lorenzo Stoakes wrote: >>> On Mon, Jun 30, 2025 at 02:59:45PM +0200, David Hildenbrand wrote: >>>> Currently, any user of page types must clear that type before freeing >>>> a page back to the buddy, otherwise we'll run into mapcount related >>>> sanity checks (because the page type currently overlays the page >>>> mapcount). >>>> >>>> Let's allow for not clearing the page type by page type users by letting >>>> the buddy handle it instead. >>>> >>>> We'll focus on having a page type set on the first page of a larger >>>> allocation only. >>>> >>>> With this change, we can reliably identify typed folios even though >>>> they might be in the process of getting freed, which will come in handy >>>> in migration code (at least in the transition phase). >>>> >>>> In the future we might want to warn on some page types. Instead of >>>> having an "allow list", let's rather wait until we know about once that >>>> should go on such a "disallow list". >>> >>> Is the idea here to get this to show up on folio dumps or? >> >> As part of the netmem_desc series, there was a discussion about removing the >> mystical PP checks -- page_pool_page_is_pp() in page_alloc.c and replacing >> them by a proper page type check. >> >> In that case, we would probably want to warn in case we get such a netmem >> page unexpectedly freed. >> >> But, that page type does not exist yet in code, so the sanity check must be >> added once introduced. > > OK, and I realise that the UINT_MAX thing is a convention for how a reset > page_type looks anyway now. > >> >>> >>>> >>>> Reviewed-by: Zi Yan >>>> Acked-by: Harry Yoo >>>> Signed-off-by: David Hildenbrand >>>> --- >>>> mm/page_alloc.c | 3 +++ >>>> 1 file changed, 3 insertions(+) >>>> >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index 858bc17653af9..44e56d31cfeb1 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -1380,6 +1380,9 @@ __always_inline bool free_pages_prepare(struct page *page, >>>> mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1); >>>> page->mapping = NULL; >>>> } >>>> + if (unlikely(page_has_type(page))) >>>> + page->page_type = UINT_MAX; >>> >>> Feels like this could do with a comment! >> >> /* Reset the page_type -> _mapcount to -1 */ > > Hm this feels like saying 'the reason we set it to -1 is to set it to -1' :P Bingo! Guess why I didn't add a comment in the first place :P > > I'd be fine with something simple like > > /* Set page_type to reset value */ "Reset the page_type (which overlays _mapcount)" ? > > But... Can't we just put a #define somewhere here to make life easy? Like: Given that Willy will change all that soon, I'm not in favor of doing that in this series. -- Cheers, David / dhildenb