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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EFAFCA0EDC for ; Thu, 14 Aug 2025 23:28:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2CAFE9001F2; Thu, 14 Aug 2025 19:28:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 255309001D5; Thu, 14 Aug 2025 19:28:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 16AE29001F2; Thu, 14 Aug 2025 19:28:05 -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 0108E9001D5 for ; Thu, 14 Aug 2025 19:28:04 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 87940117FAE for ; Thu, 14 Aug 2025 23:28:04 +0000 (UTC) X-FDA: 83776953288.01.540A83F Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf29.hostedemail.com (Postfix) with ESMTP id DAF58120018 for ; Thu, 14 Aug 2025 23:28:02 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=2nc3wY6H; spf=pass (imf29.hostedemail.com: domain of akpm@linux-foundation.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1755214082; 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=MEAN8shHJQNqQSxh89+okz6oC53z2wcJeKfPPXsVYNA=; b=Y0OBwhF83vJjBm0zuGToLXy8isAt5aUNF0iMK5SD8b6sQcSWTUpdfIIoa1wfMajNXnFm2Q akftItPpJfdYPK+lrHyMxnUJWbURI47vSCR9gIM0B4CGQN4AH9ZeJV0dpdOnwTAV6QwfIG 7U7FCt1QF2QY6CcDT/ca+NQh7nuEIZc= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=2nc3wY6H; spf=pass (imf29.hostedemail.com: domain of akpm@linux-foundation.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1755214082; a=rsa-sha256; cv=none; b=bK87C8Cg4Uu97iOB+sS1Jy0P/f+836bLvN3R+VlbLquClxKerjl3DngXNIS+sEgB3746Vb 2s2tb7u5YeGOY0sK/xxXZRQtv+GVuCErkSjBcMflM5gqkM+OLJufQwQqtkwkxoVlzRdhev Efqkkb4yrEYfapXuFnaLYLGY968RO1o= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 25088A570D7; Thu, 14 Aug 2025 23:28:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6933C4CEED; Thu, 14 Aug 2025 23:28:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1755214081; bh=RKMPJD91oygjixSsHWj5e0vCdzOp27ndBzqTMRaZ2B4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=2nc3wY6HZVO3TgsWr3n8qKoRazbe/rFSYW3Vu93F4/XRHsdO3EVO88kWu5LBU/OvL A86xKo2De+y2rzau5wNNTNkps2GmviyfmIGMDqH+wkOPjtgagU6NOLcp3/dL2HwaRA Swry8zQyOTYUXdG5XbXofKKu+LctVQ/C9k25bh/4= Date: Thu, 14 Aug 2025 16:28:01 -0700 From: Andrew Morton To: Anshuman Khandual Cc: "Herton R. Krzesinski" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/debug_vm_pgtable: clear page table entries at destroy_args() Message-Id: <20250814162801.08ece6844de66ac43af5224f@linux-foundation.org> In-Reply-To: <5e5f45c1-e813-4900-8fad-2ed0dc067468@arm.com> References: <20250731214051.4115182-1-herton@redhat.com> <5e5f45c1-e813-4900-8fad-2ed0dc067468@arm.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: mq7r4eqawzo5kjkdn8twdwakedf7onum X-Rspam-User: X-Rspamd-Queue-Id: DAF58120018 X-Rspamd-Server: rspam01 X-HE-Tag: 1755214082-764886 X-HE-Meta: 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 Ad4ER/mI nDF8rLZnSkZaDJz2bQ3o0FEmPa4Eld+dNPexTwFONy4MK+jzcWMh5gIYXOM6dqkfbFEw7yseAt2f2fdHw8IgiOkhU5FpKCQC1td7q1+ZR9TlBUbBCg+g7qcFHs1G1qRKFS05XwMBmuO8y/mlVY50MaPUyMgmJXAUWILBUfnTrBknSaC72ipYBm6Lluw2IX3HH2sJGmzcsOauEu1cQp8sY6pmhJmTKQRb0z4NA3ut6wYe4QwuVdAZogW9x/QPl3b9bIDsNEudA4mYx/pHzDMnDWJm6u3F/pF5oiRK7kGN97/NxnVt8Z8aQm8O/IyEXcaH7745tFOe34D0AN2/F7LSZLYbwLf0bpz++jZvz 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 Thu, 14 Aug 2025 16:16:03 +0530 Anshuman Khandual wrote: > On 01/08/25 3:10 AM, Herton R. Krzesinski wrote: > > The mm/debug_vm_pagetable test allocates manually page table entries for the > > tests it runs, using also its manually allocated mm_struct. That in itself is > > ok, but when it exits, at destroy_args() it fails to clear those entries with > > the *_clear functions. > > > > The problem is that leaves stale entries. If another process allocates > > an mm_struct with a pgd at the same address, it may end up running into > > the stale entry. This is happening in practice on a debug kernel with > > CONFIG_DEBUG_VM_PGTABLE=y, for example this is the output with some > > extra debugging I added (it prints a warning trace if pgtables_bytes goes > > negative, in addition to the warning at check_mm() function): > > This has been on linux-next for almost last two weeks now and > no problem has been reported. So I guess it's all good. > [top-posting repaired] Thanks, I'll move this into the next batch for sending into mainline.