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 6380FC636D6 for ; Thu, 23 Feb 2023 14:59:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AC57A6B0071; Thu, 23 Feb 2023 09:59:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A75F66B0074; Thu, 23 Feb 2023 09:59:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 916316B0075; Thu, 23 Feb 2023 09:59:50 -0500 (EST) 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 8200B6B0071 for ; Thu, 23 Feb 2023 09:59:50 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 39930AAF91 for ; Thu, 23 Feb 2023 14:59:50 +0000 (UTC) X-FDA: 80498866140.30.BCD7739 Received: from mail-pl1-f181.google.com (mail-pl1-f181.google.com [209.85.214.181]) by imf13.hostedemail.com (Postfix) with ESMTP id 4E2C320010 for ; Thu, 23 Feb 2023 14:59:48 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=EB6dxFuO; spf=pass (imf13.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.214.181 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1677164388; 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=k+yWMvIWvw3WCrNeIHfg2T45OrUG0bC11D4EFok9F+M=; b=WVBcWZGNPsPfEeRjsFNaTdHr+Hb0dhaGRFFak0kOFAS6cnJl2pmHQPuixQYp5vg+4eyuO1 xdRFhkfrxe2asDPRC8m7qzFJ9+gLflMHLbyq5HLm9tL2oW6559HTaQ8NMAVjvhWztCMD5e ZFEYnEgRqTdUAkFDdbkLd1vdt339Ng0= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=EB6dxFuO; spf=pass (imf13.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.214.181 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1677164388; a=rsa-sha256; cv=none; b=MMK7JeONrfPtdiiMPQPL5VH/l0Qz5QUipK3dxcNLFBq1zQs06QeBZSq00AA26uOn+XX/LB KwFDdMse0rY2Z+jVqeHhWPPGl8oTt/AUMc1iidBuhJ6hvAhkvWPPdgtoSkGA76ufIAANiZ 9xvQJ3OTeWjuQGHc5hC52znfRc0XFQ8= Received: by mail-pl1-f181.google.com with SMTP id ky4so14394220plb.3 for ; Thu, 23 Feb 2023 06:59:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=k+yWMvIWvw3WCrNeIHfg2T45OrUG0bC11D4EFok9F+M=; b=EB6dxFuO49E9hfnx+Osyz4QjHI3/kf2CZqPTbL8bZbPI2QTYpJp+BuVJf6x9/Op3aS xof+1Uoax1p7nvbELL+hvfbo39TWfpBmEBoy9EpUsAQdrTSvZuTrHRoWXL0gdYKaEor+ FlUMT4ZM537FZvyLzQVS2uN0IxwQHFIi6aHEt02yLOvzx/nI4cU6h6Jhn6sPqf2zGz3q 7n1Fj4k/PR8q2dQfzWmocEZdEerzfVqSvdFp8in5t8rCq1veO/qkTc35xDsvKZ7O1cgU codFdh6jBnohjFOUx2BlZiCyA2YSs+IROp6V+lyMbfz4+T3nV1nwcz5dHnaW98oy8QVz yOZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=k+yWMvIWvw3WCrNeIHfg2T45OrUG0bC11D4EFok9F+M=; b=KaaRYzOLxcyQXDAmSu5Uy73aRfgddZCU8mlUkX4i+5zmIWIXibeerq7ligi9VOF9oQ JKUgNkVtAF+6qavGaCxUXUf51AHThe6f9lFAw8VLAoDD93XfNAG/Y4eKJ0Mds/6/2mV1 /+Icpl+u6+jnfyw1bzmJOx7Iweb7fHOSqrMdTNRi8XKaw9org+rrppz0qB8QQZ/mVr8M k6IymiZSHPnVxsbXXhTkNuN3LjwnlMYTT9qRYME13A4HD2NCBrGfECBOVwDNZsYzllCc vx1WaTvRHTmuYhLcbMe9WG+eIxjQx0sOnI0H1tSMYgeU7xYQQa4zF0H0RFggRnaZKfSX nqmw== X-Gm-Message-State: AO0yUKVc4InGLprDYLX4lTXazDcRGeAT0t9nKMHUaVcfbJTSJuslQZe0 Q9hHpbjmyQNqCfe9QqDVddc= X-Google-Smtp-Source: AK7set/Qc2kRq6mVoIFJONVn7gWNZxeDHePlIGkq7CYhB6h9Zfh2pnK8s5XWdm4snMLVlByeQRXokw== X-Received: by 2002:a05:6a20:3d0c:b0:c7:1bac:6ef9 with SMTP id y12-20020a056a203d0c00b000c71bac6ef9mr12306390pzi.46.1677164386983; Thu, 23 Feb 2023 06:59:46 -0800 (PST) Received: from localhost ([2400:8902::f03c:93ff:fe27:642a]) by smtp.gmail.com with ESMTPSA id bm2-20020a056a00320200b005ac419804d5sm1703160pfb.98.2023.02.23.06.59.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Feb 2023 06:59:46 -0800 (PST) Date: Thu, 23 Feb 2023 14:59:34 +0000 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org, mingo@redhat.com, will@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, chriscli@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, rppt@kernel.org, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, leewalsh@google.com, posk@google.com, michalechner92@googlemail.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v3 16/35] mm/mmap: write-lock VMAs before merging, splitting or expanding them Message-ID: References: <20230216051750.3125598-1-surenb@google.com> <20230216051750.3125598-17-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: nbqug5jm1ik6pxtucbrf6pwahiq8kwhh X-Rspam-User: X-Rspamd-Queue-Id: 4E2C320010 X-Rspamd-Server: rspam06 X-HE-Tag: 1677164388-196972 X-HE-Meta: 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 +v1q9XCg VYK1Yfozw0NHJ7g5/3G80UsBxeAvlEymUySodEtmrq7dj77Mnfaqcekf9yOVkQXZSZvdGLaDR8i9de+TzCiTbwH1F6mB/fqesPJ7LcI2J9UQlJM+DCAj1ngElxcjczx9R5SCBiLjKG7m0us3G1vqbh0Ps6dWkP+YdmwhvbemBR6xxXzqTb5oNePgZzh2Ps6xucY2C4lG8304nEzrTpe7MHSoyWb3mNpLpuX49pL/IFg2MrTj6gScdWzL/CGYdM/yTNz6p5Xd7E08LsTs890fGTfeg8mpLvZE+RrNiSa0j6WsjbeECU4nhlHUJ+l5yfgAw5SASm2dmXDSaDp4bxZ7+FpnJW4BFX1DO0XV1BUrXMqBurMeBu5zDDkI+s4owrGTzZTTKVJL0YlLeWe/AzoANd+2QllLRPTb4KSvAVAs0AvPP80SaOkgChtCA5AQ9vqwhaXWZZYwC1p0eBz0= 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: On Thu, Feb 23, 2023 at 02:51:27PM +0000, Hyeonggon Yoo wrote: > On Wed, Feb 15, 2023 at 09:17:31PM -0800, Suren Baghdasaryan wrote: > > Decisions about whether VMAs can be merged, split or expanded must be > > made while VMAs are protected from the changes which can affect that > > decision. For example, merge_vma uses vma->anon_vma in its decision > > Did you mean vma_merge()? > > > whether the VMA can be merged. Meanwhile, page fault handler changes > > vma->anon_vma during COW operation. > > Write-lock all VMAs which might be affected by a merge or split operation > > before making decision how such operations should be performed. > > > > It doesn't make sense (to me) to update vma->anon_vma during COW fault. > > AFAIK children's vma->anon_vma is allocated during fork() and > page->anon_vma is updated on COW to reduce rmap walking because it's now > unshared, no? > > As patch 26 just falls back to mmap_lock if no anon_vma is set, > I think we can assume nothing updates vma->anon_vma (and its interval > tree) if we are holding mmap_lock in write mode. *Not interval tree, as it can be modified by other processes* > > Or am I missing something? > > -- > Regards, > Hyeonggon >