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 AC432EC1EB3 for ; Thu, 5 Feb 2026 13:10:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ECAE66B0089; Thu, 5 Feb 2026 08:10:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E4DF46B0092; Thu, 5 Feb 2026 08:10:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D22E86B0093; Thu, 5 Feb 2026 08:10:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id BD33E6B0089 for ; Thu, 5 Feb 2026 08:10:51 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 70575B9EAF for ; Thu, 5 Feb 2026 13:10:51 +0000 (UTC) X-FDA: 84410437902.14.B42A702 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf09.hostedemail.com (Postfix) with ESMTP id 628BC14000D for ; Thu, 5 Feb 2026 13:10:49 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=pNYfAeQa; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf09.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1770297049; 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=kqcpq1/LMRNsAtpRSbNB60qL1vcRdGvx5RXelBDv3v0=; b=E85t/C+I4HNjMx+dhrtooYkj8qF4iMpOQNJlzjyo9gLZpx2TcS1FnIBVyjcNJPOpEw9BSe rNXiMNXRIFnPwQW7Ihv6n8GD+2KrvEc8QXYENT2s6LAAYoaXDf4UtzlB8q1MxyAO8rAEVq lAYzy97Io+9Vltkqz6VqplW1UwF9jGo= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770297049; a=rsa-sha256; cv=none; b=crq1bVzYnlYH+EfFcQp47PMjRwBuqy9jP75hced3WDfjhg9MdxPZ50zROurTQ6fnCn8EGO VIwPt2dpxt9sEz/KqSdNPR2wkouX9TLOUrTrvffeUdEp8xA7K+eFA1xAYdv8qfHX7EcdRO zVqjWqsXy/YhB0qkZcSllvq2G6OHcp4= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=pNYfAeQa; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf09.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 21812433B5; Thu, 5 Feb 2026 13:10:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1EFC0C4CEF7; Thu, 5 Feb 2026 13:10:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770297048; bh=YNe9Nz9GlYTd64O1KTiTpwt9/xT1kD1kmstkqnvmOSI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=pNYfAeQaHzQS4JAIIf5RMJS4M1jrbWEl3KdV5wQ1CVfmAFYOtRX+59SIn8fmPO8Ex tkfXAh3SXYC3mzPHaYTYbNsTm8rtvbpWyuIcuhhDdcNdq377k6vzTZdarqvtilL3D4 Xf7+yiULCpU1+aEzuPb0FLB9CQSTB8MvWMkcFMDB5mJWXPUZ0ommmMGYPHmT6kL3rY qyMG/T2JtOKIm/hWkO7u/asLSIi4rUjArZSx8eVYVe3SeX/U9MUJb01oH/jG6auYNX sdh+Fq9oU+SuPthWrlrJpd2rDQNhsEp6q9NPXTzVBkBmuBLwpHUR29VvLiXSZaTSkg 51OS4qEEhW6Pg== Message-ID: Date: Thu, 5 Feb 2026 14:10:40 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv6 08/17] mm: Make page_zonenum() use head page To: Kiryl Shutsemau , Andrew Morton , Muchun Song , Matthew Wilcox , Usama Arif , Frank van der Linden Cc: Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org References: <20260202155634.650837-1-kas@kernel.org> <20260202155634.650837-9-kas@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: <20260202155634.650837-9-kas@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 628BC14000D X-Stat-Signature: h3rxx3akzofo8sk1rjtydtkezdwf69jq X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1770297049-156731 X-HE-Meta: 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 slehrSZF eFdgUgn8CrKDTmwvl0/sQz6h1nWgcT1gg5nh5GcN+cwSGgPuaZPAdPCHccodRV5IE+CDvHpX+lqfdO3Tvx6c+yv1NzTnq/EoYHnGr78+RhOuFadkJTYHVZWmkEFbxxWL+L1kdvYZ5izSvm8Ogpqiwsa1N2pEi2S6GZibgANeQ9QP0gS1NFQa6pibgUS98DdtksBf8Dh+lXclDIalY0ipZKTSrtYRLiw4wPU41EDB00PTXk2QOb2elCfVjyX0WD+cv6s8DsKpblV047Iyp5PzFYLReAPQbfDhKvQD1KOAC5bOuNrgLnOlRZuGocHt8RvNgpxmqxsR4KHB+aVpkQW4PAXwhxk+c4gzpfSGq 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 2/2/26 16:56, Kiryl Shutsemau wrote: > With the upcoming changes to HVO, a single page of tail struct pages > will be shared across all huge pages of the same order on a node. Since > huge pages on the same node may belong to different zones, the zone > information stored in shared tail page flags would be incorrect. > > Always fetch zone information from the head page, which has unique and > correct zone flags for each compound page. > > Signed-off-by: Kiryl Shutsemau > Acked-by: Zi Yan > --- > include/linux/mmzone.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index be8ce40b5638..192143b5cdc0 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1219,6 +1219,7 @@ static inline enum zone_type memdesc_zonenum(memdesc_flags_t flags) > > static inline enum zone_type page_zonenum(const struct page *page) > { > + page = compound_head(page); > return memdesc_zonenum(page->flags); We end up calling page_zonenum() without holding a reference. Given that _compound_head() does a READ_ONCE(), this should work even if we see concurrent page freeing etc. However, this change implies that we now perform a compound page lookup for every PageHighMem() [meh], page_zone() [quite some users in the buddy, including for pageblock access and page freeing]. That's a nasty compromise for making HVO better? :) We should likely limit that special casing to kernels that really rquire it (HVO). -- Cheers, David