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 89820C021B1 for ; Thu, 20 Feb 2025 18:53:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0A4B92802EB; Thu, 20 Feb 2025 13:53:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 055942802BD; Thu, 20 Feb 2025 13:53:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E37F42802EB; Thu, 20 Feb 2025 13:53:25 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id C6B172802BD for ; Thu, 20 Feb 2025 13:53:25 -0500 (EST) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id EC53E53E5C for ; Thu, 20 Feb 2025 18:53:24 +0000 (UTC) X-FDA: 83141221128.21.BA29621 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by imf30.hostedemail.com (Postfix) with ESMTP id 700D180012 for ; Thu, 20 Feb 2025 18:53:22 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b="cO/HoZGB"; spf=pass (imf30.hostedemail.com: domain of hca@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=hca@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1740077602; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=/9sRpAZ9G3ZPyhkT4SYRP5eAvs3BmrFCqGMSaKHucN4=; b=Z/i5bPvvlHJ1NmwF/A2hOGfZlBABN2sfuhINfD8b2M5miqTnAWBWQ8oG2pEGVlYxHlbLrW 5+/vTvwgKSTqV1MVkUX5ZMexYWcLIajymMz6xCHgijtp5rwaGcRr0zoN3SWe2TBX2UwDqg bm1yc7TBvPqcgo4Ah8RMORCjkp+y4YA= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b="cO/HoZGB"; spf=pass (imf30.hostedemail.com: domain of hca@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=hca@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1740077602; a=rsa-sha256; cv=none; b=Yvb4EeQpUilIKJXg53vxPJ9tbxu9mjmGQK5uVzS2IUpbRWeH44FPdNHaSWRxcFBx+rfjqU 056u4RBbUf8gNIhIvwE+PfX6upyr7C1EZuxA9zftPRDtsC0Ep4BjQvGMTGkES8WFdvB0wk OfimtCHaSTvToPA9ErS/7LF2JbFSiKc= Received: from pps.filterd (m0356517.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 51KH1dWO013458; Thu, 20 Feb 2025 18:53:12 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-type:date:from:in-reply-to:message-id:mime-version :references:subject:to; s=pp1; bh=/9sRpAZ9G3ZPyhkT4SYRP5eAvs3Bmr FCqGMSaKHucN4=; b=cO/HoZGBBDgyQ3+wAOCIEngTbBbh+7fO13/1YamnWNXEil u8zaNKFRabvG/FSoNrXbM3nmJitWZ4wTJD/5oHnICYWLfKWYQpfay+B+3UmNLi4a wEEHnsfHIma02MGEG+7IkYImPzHjA9t3R1erwYdh5bW/EPDJf8ctDuhhwnl/IZVC Q1xajmxr5hVEKaSmjFKS6IPrUO1NoFg0s2vDnNaxoBzRz+WMGEV/hL/MJA3zF38Q yVAGP84ZxD8GAzVMcMCs+99x9vl1ngr0vduaVeXoDxxfWXDKhUhLn0RrqKcDupM6 TmIY7yfKHiKng16RNt3tfi400kkyxJ7FnoVXJGaA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 44wreadapw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 20 Feb 2025 18:53:12 +0000 (GMT) Received: from m0356517.ppops.net (m0356517.ppops.net [127.0.0.1]) by pps.reinject (8.18.0.8/8.18.0.8) with ESMTP id 51KIrBX4004848; Thu, 20 Feb 2025 18:53:11 GMT Received: from ppma23.wdc07v.mail.ibm.com (5d.69.3da9.ip4.static.sl-reverse.com [169.61.105.93]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 44wreadapt-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 20 Feb 2025 18:53:11 +0000 (GMT) Received: from pps.filterd (ppma23.wdc07v.mail.ibm.com [127.0.0.1]) by ppma23.wdc07v.mail.ibm.com (8.18.1.2/8.18.1.2) with ESMTP id 51KI7x6h005826; Thu, 20 Feb 2025 18:53:10 GMT Received: from smtprelay02.fra02v.mail.ibm.com ([9.218.2.226]) by ppma23.wdc07v.mail.ibm.com (PPS) with ESMTPS id 44w02xkn49-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 20 Feb 2025 18:53:10 +0000 Received: from smtpav07.fra02v.mail.ibm.com (smtpav07.fra02v.mail.ibm.com [10.20.54.106]) by smtprelay02.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 51KIr8gA39846268 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 20 Feb 2025 18:53:08 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0D4CC20043; Thu, 20 Feb 2025 18:53:08 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3CEE020040; Thu, 20 Feb 2025 18:53:06 +0000 (GMT) Received: from osiris (unknown [9.171.52.26]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTPS; Thu, 20 Feb 2025 18:53:06 +0000 (GMT) Date: Thu, 20 Feb 2025 19:53:04 +0100 From: Heiko Carstens To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, peterz@infradead.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, david.laight.linux@gmail.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, richard.weiyang@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v10 12/18] mm: replace vm_lock and detached flag with a reference count Message-ID: <20250220185304.8313A7d-hca@linux.ibm.com> References: <20250213224655.1680278-1-surenb@google.com> <20250213224655.1680278-13-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250213224655.1680278-13-surenb@google.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: M-vGldV3REsWVvBOwJDEiV9dEv7a8khD X-Proofpoint-GUID: LuM4Ib9qTs5DatP339mkaUEvtZKh3JTf X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-20_08,2025-02-20_02,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 suspectscore=0 bulkscore=0 mlxscore=0 adultscore=0 spamscore=0 impostorscore=0 phishscore=0 clxscore=1011 lowpriorityscore=0 mlxlogscore=842 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502100000 definitions=main-2502200128 X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 700D180012 X-Stat-Signature: sfn4djfna71itskmex6xhue7cdwem9xo X-HE-Tag: 1740077602-516944 X-HE-Meta: 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 TdyaFZ1z 7VhCruD1gAjedjWhGglnWgwDDN6IWb+ZEYfmODPO5lfb7AgyDf1rwtbtRGXIgF0nDypU8nq9bKFauIK1dXzMLJWCPFEMgBihBp3Ybg2gZ/+b/j9OLuqyxj6MgCWNzVYpP3W9svfSAJGKJZ6QiU/LpouaJ8hFg6zC0jd/A5HoRRH+KPAqYXwKzzYwP+2EGSiPG8WdjVyYOp6J4NpFt7Q8YDrD0cF4B+xjK28oc+IX18vto7ZxOq+LGfy0HzkpWA0wm91sJxBk869/ckDluSjDiaYTGGLGY/BoN304+0d619n0jHgBS23O0CB1rtrKslAi46YrOaDadq+U49WZRbd4CPVgywMsUpA3fkqaDmgM8FB4cs2ajJrMqwc6yNTYHbHm9fcxTCN1FQ24u6V2PndXQD/vppo0u4IkRTPo79Z8koA9/N/U= 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, Feb 13, 2025 at 02:46:49PM -0800, Suren Baghdasaryan wrote: ... > While this vm_lock replacement does not yet result in a smaller > vm_area_struct (it stays at 256 bytes due to cacheline alignment), it > allows for further size optimization by structure member regrouping > to bring the size of vm_area_struct below 192 bytes. > > Suggested-by: Peter Zijlstra > Suggested-by: Matthew Wilcox > Signed-off-by: Suren Baghdasaryan > --- > Changes since v9 [1]: > - Use __refcount_inc_not_zero_limited_acquire() in vma_start_read(), > per Hillf Danton > - Refactor vma_assert_locked() to avoid vm_refcnt read when CONFIG_DEBUG_VM=n, > per Mateusz Guzik > - Update changelog, per Wei Yang > - Change vma_start_read() to return EAGAIN if vma got isolated and changed > lock_vma_under_rcu() back to detect this condition, per Wei Yang > - Change VM_BUG_ON_VMA() to WARN_ON_ONCE() when checking vma detached state, > per Lorenzo Stoakes > - Remove Vlastimil's Reviewed-by since code is changed This causes crashes (NULL pointer deref) with linux-next when running the ltp test suite; mtest06 (mmap1) test case. The bug seems to be quite obvious: > @@ -6424,15 +6492,18 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, > if (!vma) > goto inval; > > - if (!vma_start_read(vma)) > - goto inval; > + vma = vma_start_read(vma); > + if (IS_ERR_OR_NULL(vma)) { ^^^^^^^^^^^^^^^^^^^ > + /* Check if the VMA got isolated after we found it */ > + if (PTR_ERR(vma) == -EAGAIN) { > + vma_end_read(vma); ^^^^^^^^^^^^^^^^