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 D8E53C79FB6 for ; Wed, 9 Sep 2026 13:52:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D08BC6B008A; Wed, 9 Sep 2026 09:52:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CC8706B008C; Wed, 9 Sep 2026 09:52:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BDE9A6B0092; Wed, 9 Sep 2026 09:52:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8E0A46B008A for ; Wed, 9 Sep 2026 09:52:26 -0400 (EDT) Received: from smtpin25.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id D5FBB80207 for ; Wed, 9 Sep 2026 13:52:25 +0000 (UTC) X-FDA: 85194363450.25.06555CE Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf16.hostedemail.com (Postfix) with ESMTP id 26E6D18000E for ; Wed, 9 Sep 2026 13:52:24 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="Rc/XpYW6"; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 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=1788961944; 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=Kmq63K6J6IaLLBR/41fmMzftkZbpiaUzb2YtjOSoo0U=; b=PJ9pPXZsSJMld31mBheRmlx3UqVbJyHqa0oND9n09DM6IV/Ph+gL8DpSKKxzmdrAMJV9em pUPbSPw2gIjKfMCiO3Lyug2FrMX3JFvfZGsmqtt7sjly8VXqm86FF50Ms61m4kp4YMKD7g Qe3hWZMYjf+CQMj2gIeJMvbNFbrgJIk= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788961944; b=BrTvnbN4ClT3T+mbaeL0H/mhbAANMzIMPAwc9dncXB16UajLcnb84k5jpZLYSn6FOymUhW tFXqrOM6QZ96z+qjUg9b9kLPe+fhnfivD6gs3Lwym2imuLKwNcI3ttfVrBXqR6JNNJqodc UNQGVroMx+X1zZ27vyB0MiSeh4E5gAM= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="Rc/XpYW6"; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id A774560211; Wed, 9 Sep 2026 13:52:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0CC151F00A3D; Wed, 9 Sep 2026 13:52:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788961943; bh=Kmq63K6J6IaLLBR/41fmMzftkZbpiaUzb2YtjOSoo0U=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Rc/XpYW65T8AigmjkUpYPLbHSZ9iXw+bBBHqj4ua9Q2oTPZXtYWZGsYw4P+UOFXEn 5Bttkz7GfSPJr/Vjdm5880Q9nk+FmJIrh5DInsvEW1R5FM8DmJvaGhSsNuPMxE7E1y JgP9Q9tE4VzRuEtYnS3oJRN7Xabxv/7BEH82ph2uywANQiWQQsgn2MNdXG6FLrSAj7 4Ljse3qoohE7fRIu1f2osn6NaKOpTmebO5+K5E8/dADRwqdyg/T+JkE7eOpCSuov0s foVOnwwMQCXZ7GMCSmMeW3lfqC47NeyncHaRAI72S/lqru99uE2/3QDEKaDAzWgziO 57ZeCyYKJlxBg== Message-ID: <6067ba05-82e6-434c-b717-93ea2fb7d853@kernel.org> Date: Wed, 9 Sep 2026 15:52:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/8] mm/huge_memory: add a comment to the open-coded swap entry To: Tal Zussman , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Lance Yang , Usama Arif , Kiryl Shutsemau , Lorenzo Stoakes , Rik van Riel , Vlastimil Babka , Harry Yoo , Jann Horn , Johannes Weiner , Yosry Ahmed , Chengming Zhou , Catalin Marinas , Will Deacon , Mark Rutland Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20260908-folio_swap_entry-v2-0-ee6d01dfa5e1@columbia.edu> <20260908-folio_swap_entry-v2-2-ee6d01dfa5e1@columbia.edu> 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: <20260908-folio_swap_entry-v2-2-ee6d01dfa5e1@columbia.edu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 26E6D18000E X-Stat-Signature: gki9choso8uryqfw6x8p4ayfs6cruxb5 X-HE-Tag: 1788961944-793582 X-HE-Meta: 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 d2uCRo4+ fQqRQCsl16GctDNxEKuBDovjd5QAp/5Y8p4C7bhK6BqGCGeXGaJQ1OgJu9DJSQ7Dj91PCDkmzRDxhsgMkA1zkwthe4d4GaW4kh9fj51LNiNI1pqteUYJQ0cu6GTWy1/CBhnmSGSd3ozfUsvLa404TUpSA+ykDOVsBopcbnlDQN312TO9gwDyAg0leSfmJymeZq0Kmexo4xC096OW/aWsll3Trv8gHm0Eg8E3CaxC4zDe2HXtuqi3SQcuS+Wyfh2Rkh0mjqBGq8AMzy9B3zYXKuoro1Z6Tn9GHiTYEb1Ind7UBBu6j8/9tzU29jbp0aVIQqxcTz7IVvIAOWzE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/8/26 17:16, Tal Zussman wrote: > The swap entry of each new folio in __split_folio_to_order() is > computed by hand from folio->swap rather than with folio_swap_entry(), > because the folio's page count is not valid while it is being split. > Add a comment explaining this. > > Signed-off-by: Tal Zussman > --- > mm/huge_memory.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index d1ce061601bc..1fabdcbd8c8f 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3763,6 +3763,10 @@ static void __split_folio_to_order(struct folio *folio, int old_order, > */ > VM_WARN_ON_ONCE_PAGE(new_folio->private, new_head); > > + /* > + * Not all folio fields are valid during a split, so open-code > + * the swap entry rather than using folio_swap_entry(). > + */ > if (folio_test_swapcache(folio)) > new_folio->swap.val = folio->swap.val + i; > > Acked-by: David Hildenbrand (Arm) -- Cheers, David