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 64996EA4E09 for ; Mon, 2 Mar 2026 14:40:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B6F396B008C; Mon, 2 Mar 2026 09:40:36 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B46696B0092; Mon, 2 Mar 2026 09:40:36 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A69216B0093; Mon, 2 Mar 2026 09:40:36 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 97BEE6B008C for ; Mon, 2 Mar 2026 09:40:36 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 423F8B6874 for ; Mon, 2 Mar 2026 14:40:36 +0000 (UTC) X-FDA: 84501384072.14.BE9CAB6 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf17.hostedemail.com (Postfix) with ESMTP id 837084000A for ; Mon, 2 Mar 2026 14:40:34 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=i3jVvCCf; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf17.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=1772462434; 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=Qa6g6TnMMEkaRKPiNfgt8jxQ7MgzSzUcxh0lMlIw+vw=; b=shUGI6TgaZquU+E7JY+98yY8kjNPe6GyQX6xI5rCmM0AWQibF6InKOzaVHICaip3zvUBXJ IyUKdKePZj2aRr0oZjLzprQx4Sq/Cgah2tEBq1hDE4jnnVYOEKpjJh+N8PAFK1jFHxTzQo zLEKRF5invg8gXhRBtULWhd7+N62frA= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=i3jVvCCf; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf17.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772462434; a=rsa-sha256; cv=none; b=Dp+sBO7yoP/FrLg7CeS7i2H9dC62ZIv8/8jdwFfryAWX2mvdo9cPNStIcH5dIALlSqneWs /jyGqSFieaShkyEjj8DDd458WdfAv0XJhVnqH2BqThh1kj358agUeY7Qu6LGZA2JrAwcME 1IJaev+pZGi+NaE2C9jpKN9BZlikoGI= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id D496E60008; Mon, 2 Mar 2026 14:40:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB07CC19423; Mon, 2 Mar 2026 14:40:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772462433; bh=wpFu9y+6TnLxJpo9lrnsoN4LUcOEqD5oLyYF4BEFJyk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=i3jVvCCfvaFrhQXN+TRWNan8/m8GQBfWL/HDjS+ZSau1QmHjw2jGc1vQn2tsHxnbV miA+rIyjjUT/x3C7hSXPZ9Z1WLdHN86DQhaoUuLeAAPDbHBZ8LaQhx9SwE4G4XjGSF tLEuyQ7iz/EPQFJX9GLkf9louxvnrl6IJjkuCXGkIpj+opXB/oAA9gSBnRGJT7PNqJ t2Xm0ISLIIb6Nl78y9uUOpKF+Tq2AvR0+ycjAVlFK6hOLfy94vXI6N+45b2rUHKXdH 9GUSZrrT0jfy6OYrTTmfTKLOSPIFKl/tJ3toKQzqnFQNg1gwX7haV1FIWnYE6mF12q XCtRX1jJXIRcQ== Message-ID: Date: Mon, 2 Mar 2026 15:40:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/huge_memory: fix a folio_split() race condition with folio_try_get() To: Zi Yan , Andrew Morton Cc: Lorenzo Stoakes , Hugh Dickins , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Matthew Wilcox , Bas van Dijk , Eero Kelly , Andrew Battat , Adam Bratschi-Kaye , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org References: <20260228010614.2536430-1-ziy@nvidia.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: <20260228010614.2536430-1-ziy@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 837084000A X-Stat-Signature: j8snhfdzndz8xi4nztm6tch8h1et1a53 X-Rspam-User: X-HE-Tag: 1772462434-602680 X-HE-Meta: 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 GfyFfLJw fhfQ0ghcv15FbueqYIoiFT+k2tdl6rHfJiuv9LDae5/tKu10I17kWgDvt4xcWdXeQ77fzykDhBhS8hdaEuwo18HblzO6IGWPKjQ7eAsG9cmhgecqdO5e6OSezbqbj+fTYkfsU5EeMNCjCfO1R7nU9GyLzeCEMpWkSXMfQs2snA6yvw+rd6l69Z1GtoLJhln/B95f4VU/CwtbtLetNtwjoIDqiwN7ZG+Iu+t6/NA9IayaWekjG2C9NTjeQLEEuqyoBvoHqC1Tes0Wyev1E+Wg48U3Rj2v7gHYTpR8al6hbRLKz204qfpyCH56kUw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/28/26 02:06, Zi Yan wrote: > During a pagecache folio split, the values in the related xarray should not > be changed from the original folio at xarray split time until all > after-split folios are well formed and stored in the xarray. Current use > of xas_try_split() in __split_unmapped_folio() lets some after-split folios > show up at wrong indices in the xarray. When these misplaced after-split > folios are unfrozen, before correct folios are stored via __xa_store(), and > grabbed by folio_try_get(), they are returned to userspace at wrong file > indices, causing data corruption. > > Fix it by using the original folio in xas_try_split() calls, so that > folio_try_get() can get the right after-split folios after the original > folio is unfrozen. > > Uniform split, split_huge_page*(), is not affected, since it uses > xas_split_alloc() and xas_split() only once and stores the original folio > in the xarray. Could we make both code paths similar and store the original folio in both cases? IIUC, the __xa_store() is performed unconditionally after __split_unmapped_folio(). I'm wondering, though, about the "new_folio->index >= end" case. Wouldn't we leave some stale entries in the xarray? But that handling has always been confusing to me :) -- Cheers, David