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 7EA96C61DC4 for ; Thu, 27 Aug 2026 15:58:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 711C76B0095; Thu, 27 Aug 2026 11:58:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6C48A6B0096; Thu, 27 Aug 2026 11:58:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5654C6B0098; Thu, 27 Aug 2026 11:58:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 26F0D6B0095 for ; Thu, 27 Aug 2026 11:58:32 -0400 (EDT) Received: from smtpin08.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 9812D1A045B for ; Thu, 27 Aug 2026 15:58:31 +0000 (UTC) X-FDA: 85147506822.08.F733D49 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf31.hostedemail.com (Postfix) with ESMTP id D2D5D20008 for ; Thu, 27 Aug 2026 15:58:29 +0000 (UTC) Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=IuvYdEUG; spf=pass (imf31.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787846309; 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=j6F1CmlViOZAv7ScdpKDj4KMGRJno7AOUlTrCO7k1xM=; b=Hg0EWBENNSfFDthrKFo1HU0Ys4PZbcQ4c3wYxLHszmm0WpIS1/gmPIxWKdA3f8P5XGN7aV 4Ta55sD5UZIT4rqqKeSQbjaojRECmU7d5jH4LDaMQ8UOniXmpy4ucGFBIE+QPZIE/O5MgC dgEUTQ0qFpjHkeoVFyUspQ1jRlMLZpQ= ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=IuvYdEUG; spf=pass (imf31.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787846309; b=jNjbRlHNgahx17rJCKKGiRlBLdcaJk4shadEgvEfHmTHx866gcT/tg0lfhIb+QoPNuorfk JZVSgB8JbeZ/VX6XuzxF6BGBv0+L6EjwSzlYqVaCoS6qVD5z44kgHyaWPasZ7cdHRK2tbi 8fXiYU3W3qrYbJtIoNt5xusW18Krjjg= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 54F6C600D2; Thu, 27 Aug 2026 15:58:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3416C1F000E9; Thu, 27 Aug 2026 15:58:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787846309; bh=j6F1CmlViOZAv7ScdpKDj4KMGRJno7AOUlTrCO7k1xM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=IuvYdEUGfFZHsjDqrO3R3icx/zIgT8pMZ/kZa56FxwIxStQoFO0r0hSM8mLtTLCyN pqcjwK8SZHPICdndkn/dK6o8R9vpsFIfZUAnDvCgJpHDWNZixYX0GeRYWhxRVn0zid iROWgn+A45NWlds4wpAF6a+T6snS0vCp+WgsaOPqutp1FhQtn4ngXacsbFhEV8yRUw mT4UAAoRbw+p0YJMOZDOdIMNVrGILItRwJcAEdjziG8XqKl8HmI1Ft95TH/9j36qLB a1ucmi/HX0RRUUma2nTGd+VPWyQdBmbjAvMrzbZnwFRrpsQrpNjKkFHB+TutE0S4jy fpOmavz6Zq98A== Message-ID: <8acccec9-acd7-48e4-a461-0a3e706466c8@kernel.org> Date: Thu, 27 Aug 2026 17:58:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 02/18] mm/huge_memory: fix rejection of swap cache folios with a mapping To: Kiryl Shutsemau , kasong@tencent.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Chris Li , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Shivam Kalra , Kairui Song References: <20260821-swap-thp-cleanup-v3-0-9b43f5163238@tencent.com> <20260821-swap-thp-cleanup-v3-2-9b43f5163238@tencent.com> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: x8ayzm4p5hia1dtyih88ydnrtkawp41d X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: D2D5D20008 X-Rspam-User: X-HE-Tag: 1787846309-397462 X-HE-Meta: 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 ngt505CT KFz5av0SDZQ2l0QBkVXlWSI1WT0vx0TXcec98WB3F1bnI3Rff0H2cg2QZCFZMcgHS0bfrQ2vmDw32UrVLuDmQUckrvbCwNqVBrCtGHfI5dDEXuT3tLTfgjTES2O+XiTs72xlV4/3XU/M/m5jKRgcQ+jXQMCY0VVVqxp1F7ULLaG7aaWfBoJPRPmZDa4RIzmM+MXEZ9ARGTvp7wESc9Y4xfqfS9Rdgqg1xXkV10jq+zS1yfa8jCuD08JkNw/Nv+cO9Zphtp8y3QpiUST8/e6EuNw62uPNQ1aDomumckDhO+abvDqeqSu6HECTgMqY3Jm2qoUs1hs2gl6T9PYU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/27/26 16:33, Kiryl Shutsemau wrote: > On Fri, Aug 21, 2026 at 02:55:15AM +0800, Kairui Song via B4 Relay wrote: >> From: Kairui Song >> >> A folio in the swap cache cannot be split if it has a mapping (shmem). >> The split code does a defensive check for this in >> __folio_freeze_and_split_unmapped, after the folio ref has been frozen >> and the NR_SHMEM_THPS/NR_FILE_THPS counters have been decremented. It >> rejects the split and returns -EINVAL without unfreezing the folio or >> restoring the counters. That error path is buggy: if it is ever taken, >> it leaves the folio frozen and stuck, skews the counters, and fires >> the VM_WARN_ON_ONCE_FOLIO for a state that is actually legitimate. > > If you are going to repost this, could you make "This error path is > buggy" a new paragraph? > >> >> Check for this case up front in folio_check_splittable and return >> -EBUSY before any state is modified, so the split routine always backs >> out cleanly. >> >> Also fix a bracket style issue that checkpatch.pl keeps complaining >> about. >> >> Fixes: 00527733d0dc ("mm/huge_memory: add two new (not yet used) functions for folio_split()") >> Fixes: 714b056c8321 ("mm/huge_memory: convert VM_BUG* to VM_WARN* in __folio_split") > > This is inert bug, right? I don't think we want the commit to be > backported. I expect stable machinery to pick it up based on Fixes. > > Is there a way to express "not stable material" while keeping Fixes: in > place? In mm, stable never picks stuff up automatically. it's usually best to write in the patch description why the decision was made that it should or should not be, stable material. -- Cheers, David