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 1D4A2FCD0C6 for ; Wed, 18 Mar 2026 07:39:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 837EE6B0107; Wed, 18 Mar 2026 03:39:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7E8C66B0109; Wed, 18 Mar 2026 03:39:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6D7BA6B010A; Wed, 18 Mar 2026 03:39:06 -0400 (EDT) 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 5CA706B0107 for ; Wed, 18 Mar 2026 03:39:06 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 304761B82BC for ; Wed, 18 Mar 2026 07:39:06 +0000 (UTC) X-FDA: 84558382692.30.997C722 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf27.hostedemail.com (Postfix) with ESMTP id 596FC4000F for ; Wed, 18 Mar 2026 07:39:04 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=t6iBdeFX; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 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=1773819544; 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=Kcmyer42+YoDVl4pl/KmgE42Up2/TQolBVndvcfc71I=; b=6jG1ntM1zTeKkItp9M/s3y4tuZVW5k74yj7nxxSsnhUiqUy/3Z2axoX6HiBqDXNqYmOPHH gWleb9J8mfjv/YFsOk4XbdGWFfg/TdEg1BB9VXUAQYBF9WvWWiHMjtXY6fdPfLCZa2mOX/ zi1cxC/WvT4D3s7MCsquyaDIk6owZeE= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=t6iBdeFX; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773819544; a=rsa-sha256; cv=none; b=az7oqlEnjVoK06iMT+Ra4OWvBjWnwSyegRAnpV3C4q4I3d7Si0uLiExURIAOu9KBqugS4d XzUxpehxs1VC6qZEt59Ydb6STBqF8k40aOWGQdE1mAfllLa1de/XkwIrxpDw7TCmvRJYSM bjwB3NMOolb8hTQy7zW0jjXxJtehCcA= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 3FB824037C; Wed, 18 Mar 2026 07:39:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16B12C19421; Wed, 18 Mar 2026 07:38:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773819543; bh=zAzMUNn/kPLxwCHXe0I/zwTQQojBCM3qQBBRcS01Yi4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=t6iBdeFXKEMsoCQ85CIhXZVeL3QEMhTiEWy82sD9FBsTjxV+jPEgdxqlfrxK7HeFP +LJOJzR+xrHPphxVclFmGJruJnqnUMN2CA2frfTCbiNKJhKThV5X++tcio8ErMs2fu SPGEauRzmkyJH6lLSbkoF0lKYJwmUEmJA6Sqv76cd97mIF5HiiNlM+IRCiRTSF7HrR q98S1YidFUmflFlstLTnVZ/KHduB3PvJga0N6CJhO11ZZAbjSlJ11nceirWEXKyQHH k0RGwUfskdyrmzQZVKv344W5yGcGcZYy4nonpUdUgTxkD9CbOj1ksqQdiAl3veab2X 8tG8zgNl3mktw== Message-ID: <13624f64-a624-48ac-94b9-f43689441316@kernel.org> Date: Wed, 18 Mar 2026 08:38:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/pagewalk: fix race between concurrent split and refault To: Qi Zheng , mboone@akamai.com, Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, stable@vger.kernel.org References: <20260317-pagewalk-check-pmd-refault-v1-1-f699a010f2b3@akamai.com> <268abf39-9cd6-412e-b3ec-32fb8fea1684@linux.dev> 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: <268abf39-9cd6-412e-b3ec-32fb8fea1684@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 596FC4000F X-Stat-Signature: ixux7p3xqfdsnguu1e7myirb1j9i9boz X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1773819544-56490 X-HE-Meta: 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 rCVK1P9o qy27AN/oEeOwlJqQ3RXhKII9vpURAQuM5kwHi3uFr9ck0Ufl3WVv8rM74idZd3zGmy+uV3UX7AUaWKTolEP3LoiygJRfr2nXG+KeluDRBH3lBMh2naRh1LN3cfcS9GKNLf9nydE2HgOZLX/wbL8EmXb3VRh1cxoqGUFr+ogjFG/ViBHwXwgssTK1u26rYqXA4TUi49O2suaBVkPkovtAO4LVkmcDAQtsJnnfmAwmtk3gWwah9Ci8LQnfLToe7qV4iMDmEv/w//TVz5IJOjcAQBDLFKTQCoQiA9sJBDwauNWgsvCPPD5jcyxNgFQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> + >>       pmd = pmd_offset(pud, addr); >>       do { >>   again: >> @@ -218,12 +231,13 @@ static int walk_pud_range(p4d_t *p4d, unsigned >> long addr, unsigned long end, >>           else if (pud_leaf(*pud) || !pud_present(*pud)) >>               continue; /* Nothing to do. */ > > Why not check pudval directly here? Like the following: > As the patch description states: "This mirrors the retry logic in walk_pmd_range()." -- Cheers, David