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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 313B6CAC5A8 for ; Mon, 22 Sep 2025 14:44:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5F0268E0002; Mon, 22 Sep 2025 10:44:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 579E68E0001; Mon, 22 Sep 2025 10:44:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 41A138E0002; Mon, 22 Sep 2025 10:44:43 -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 2A3FA8E0001 for ; Mon, 22 Sep 2025 10:44:43 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id A97BDC06A0 for ; Mon, 22 Sep 2025 14:44:42 +0000 (UTC) X-FDA: 83917157604.02.363AC46 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf20.hostedemail.com (Postfix) with ESMTP id 30D6E1C0012 for ; Mon, 22 Sep 2025 14:44:40 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=M2JhCGIi; spf=pass (imf20.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=1758552280; 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=vwOZIhtF+CnAdagM2d4IT7kAjcwDptx80GYkfUL7tc0=; b=sNGyCMp7/JTQasYCy7lEdcOwmR73bi8fcDKvcmv678LXHOKoWqER8NFbYpvvUPUyufsP0x T3R9I94EFkEbSKvFos68VjnvO0a/4ImhpSi8l0r1Vvy0enb3tRhW3pZrhV5D/bewvSvvB8 T8rqVzLQdqQlVpE5afqhaozPM5xDa8A= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1758552280; a=rsa-sha256; cv=none; b=SPFQ36hxn+hDjFt0vvCl2VM0CTD2Xl0Z3tuB3UaKcgR1aBC2fTiwEBAQFBPtm69XaQV1dF 0Yc1EkL9kX61ffdkUhWm38+JklBbpwm9zJoLBuPAEVkKzDRkEGnC3bzhYFQJMsgWO21MVq 2+53i96MHNsoZOEglrCA9GzeAk2r0QU= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=M2JhCGIi; spf=pass (imf20.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 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758552279; 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=vwOZIhtF+CnAdagM2d4IT7kAjcwDptx80GYkfUL7tc0=; b=M2JhCGIi6M89yjOKMzrMgsljfCIs3HUljOF0sTylSfa8Y6e17rwboq3Fh+9R+oQTMPx+KF jqHilnIebgYP9c5JVfsRooEJ0STHP0pMN+sUxxESx0SSUYIbIDJr0CIXbkApDNwgFkcM/X ROjIAdW3ULRfa12VAW5mRJxzJ0YKqao= 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-73-LDJUzEJdN6SvLWGAPrTdKw-1; Mon, 22 Sep 2025 10:44:38 -0400 X-MC-Unique: LDJUzEJdN6SvLWGAPrTdKw-1 X-Mimecast-MFC-AGG-ID: LDJUzEJdN6SvLWGAPrTdKw_1758552277 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-3f456d4db0aso1265561f8f.1 for ; Mon, 22 Sep 2025 07:44:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758552277; x=1759157077; h=content-transfer-encoding:in-reply-to: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=vwOZIhtF+CnAdagM2d4IT7kAjcwDptx80GYkfUL7tc0=; b=GhEK14niadjW61ck4zA94RxmiBPpgExlU2Z8gaJfq+EpJt0ZnoH0GcOVAvVIAfjRNG 6RyUL3SFRHiAv3HWf9HZfFw2m3+YSdzud+m2mLNl7fsK4/1KCe6wIAXXgCUTsjQFd4TZ PmQgfOLpQh7Zp2y7GuviPATk0luyOOSkaTzJkY7OziTCB78r7hpPlLZcTeRhVz6jTv/y 8/dDTzfI4pdaEJ/+j1OK60LMe4PF8skLQFA9BQblFocd+pqy7wE9E1y9sCs4dRxiWGCx YwSK0/WgYzFVVZucSfjCyCyvYhMOEauRb1jXODQg4shujGulmtkPE2euFc+o/jEwACmB xt5A== X-Forwarded-Encrypted: i=1; AJvYcCXoI9jncdio3fx/HKTtC/y7MhdBjnqxfXNBibfumQ5LgyY8M9OFqQpLsIFvMwL8GFaVYeQ7tpS0zA==@kvack.org X-Gm-Message-State: AOJu0Yz72hxTvR/gH54Vzd52i5deMKrMKtBOmErgw/VoGsHD9hCjVEjY KNcg/By8zoMXPzk5aWYztdsc1m4LLSjozO0Vqt+K1WadnZe0Z0TSHd56DRZL4NQaD3GqE01DROO TOSrXcENCU6xLuWCVLZWkQ7uK1jT3FavqLk0qp0bTnNiNQlXt9/2K X-Gm-Gg: ASbGncvHr6xprRvtFzbW4gOEtw0YjhvCkas3Dh6AQVhfFc6NsYHjwJWsJq4OnAv5IGp Gyp5NIESUYf7+eidFpooLMrakB0TbULYZa0MUW5IENNihSPFoAmeGli9uU/kouzzJbNtOq6achH dgvUyTFs+mzjIjtd/ef9v1PA54vqntD56MPhVv+jD1YAu7f99SKEPq4kDiUh+aTCDEYjEZUuZIl KxK0vikvTOmibsBEM504ZiX5GJEEELi8qvtlsA+Ay3QjbcUkOX/t2Kp/IxJbvrSCSCQNEQxfsiU DSJW7nIV5URCEo13XQDtc2Ixsncd/d42AlfA39nnW2uhvIqFfaepd7XeNEWIu/Q7SIknLUlA2Uo M9tdwueF4g+SXQrZmO281gr4kwaHoFpgXPWcJcmVhKiVXnpBsDLd75AqHysZubvg= X-Received: by 2002:a05:6000:24c9:b0:3ea:6680:8fce with SMTP id ffacd0b85a97d-3ee8585f6e8mr11215974f8f.48.1758552277012; Mon, 22 Sep 2025 07:44:37 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHTQ9iic04xqRMwRFFl4BEGh1sQte7ezvVn6iJMb+gWyL9TDixHQdGS9iCX9Y49rrUxsEeywg== X-Received: by 2002:a05:6000:24c9:b0:3ea:6680:8fce with SMTP id ffacd0b85a97d-3ee8585f6e8mr11215953f8f.48.1758552276597; Mon, 22 Sep 2025 07:44:36 -0700 (PDT) Received: from ?IPV6:2003:d8:2f2a:e200:f98f:8d71:83f:f88? (p200300d82f2ae200f98f8d71083f0f88.dip0.t-ipconnect.de. [2003:d8:2f2a:e200:f98f:8d71:83f:f88]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45f325cec0fsm144160475e9.4.2025.09.22.07.44.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Sep 2025 07:44:36 -0700 (PDT) Message-ID: Date: Mon, 22 Sep 2025 16:44:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] mm: MAP_POPULATE on writable anonymous mappings marks pte dirty is necessarily? To: Pedro Falcato Cc: "wuyifeng (C)" , akpm@linux-foundation.org, linux-mm@kvack.org References: <17ad24e5-9ee0-4d94-be5f-3c28bd57460a@huawei.com> <8e8b4aa4-18b7-4928-a9f0-cd47a59258fc@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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: FZf8GgxPvcCWykgqlUl1dlCH5pJe2pvQZmR9ZZZmnfs_1758552277 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: 30D6E1C0012 X-Stat-Signature: e17ytrqtp47ix1f7uozyac85itdo9h3d X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1758552280-282993 X-HE-Meta: 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 0EigH+E5 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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 22.09.25 16:13, Pedro Falcato wrote: > On Mon, Sep 22, 2025 at 02:46:44PM +0200, David Hildenbrand wrote: >> On 22.09.25 11:37, Pedro Falcato wrote: > snip >>> >>>> What happens on architectures where the HW doesn't support setting the dirty >>>> bit is that performing a pte_mkwrite() checks whether the pte is dirty. If >>>> it's not dirty the HW write bit will not be set and instead the next >>>> pte_mkdirty() will set the actual HW write bit. >>>> >>>> See pte_mkwrite() handling in arch/sparc/include/asm/pgtable_64.h or >>>> arch/s390/include/asm/pgtable.h >>>> >>>> Of course, setting the dirty bit either way on later access comes with a >>>> price. >>> >>> Ah, yes, the details were a little fuzzy in my head, thanks. >>> I'm trying to swap in (ha!) the details again. We still proactively mark anon >>> folios dirty anyway for $reasons, so optimizing it might be difficult? Not sure >>> if it is _worth_ optimizing for anyway. >> >> I remembered the same thing (proactively mark anon folios dirty) but I >> didn't easily spot it in the code. Did you spot it? >> >> I only found the folio_mark_dirty() calls when unmapping anon pages and we >> stumble over a dirty pte. >> > > In shrink_folio_list(): > if (folio_test_anon(folio) && folio_test_swapbacked(folio)) { > if (!folio_test_swapcache(folio)) { > /* ... */ > /* > * Normally the folio will be dirtied in unmap because its > * pte should be dirty. A special case is MADV_FREE page. The > * page's pte could have dirty bit cleared but the folio's > * SwapBacked flag is still set because clearing the dirty bit > * and SwapBacked flag has no lock protected. For such folio, > * unmap will not set dirty bit for it, so folio reclaim will > * not write the folio out. This can cause data corruption when > * the folio is swapped in later. Always setting the dirty flag > * for the folio solves the problem. > */ > folio_mark_dirty(folio); > } > } > > So we assume the folio is dirty due to races with MADV_FREE. Seems like a > somewhat heavy handed solution, but I guess it works nicely for 99.9% of cases. Thanks, yeah that makes sense. Whenever we add a folio to the swapcache we mark it dirty, so it's guaranteed that whatever content it had (even if just zeroes) will be written out. -- Cheers David / dhildenb