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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3AF1C3279B for ; Mon, 2 Jul 2018 14:05:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 95D6525E3A for ; Mon, 2 Jul 2018 14:05:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 95D6525E3A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752526AbeGBOFO (ORCPT ); Mon, 2 Jul 2018 10:05:14 -0400 Received: from mx2.suse.de ([195.135.220.15]:51512 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752355AbeGBOFF (ORCPT ); Mon, 2 Jul 2018 10:05:05 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 5034CAD26; Mon, 2 Jul 2018 14:05:04 +0000 (UTC) Date: Mon, 2 Jul 2018 16:05:02 +0200 From: Michal Hocko To: Andrew Morton Cc: Yang Shi , willy@infradead.org, ldufour@linux.vnet.ibm.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, tglx@linutronix.de, hpa@zytor.com, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC v3 PATCH 4/5] mm: mmap: zap pages with read mmap_sem for large mapping Message-ID: <20180702140502.GZ19043@dhcp22.suse.cz> References: <1530311985-31251-1-git-send-email-yang.shi@linux.alibaba.com> <1530311985-31251-5-git-send-email-yang.shi@linux.alibaba.com> <20180629183501.9e30c26135f11853245c56c7@linux-foundation.org> <084aeccb-2c54-2299-8bf0-29a10cc0186e@linux.alibaba.com> <20180629201547.5322cfc4b52d19a0443daec2@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180629201547.5322cfc4b52d19a0443daec2@linux-foundation.org> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 29-06-18 20:15:47, Andrew Morton wrote: [...] > Would one of your earlier designs have addressed all usecases? I > expect the dumb unmap-a-little-bit-at-a-time approach would have? It has been already pointed out that this will not work. You simply cannot drop the mmap_sem during unmap because another thread could change the address space under your feet. So you need some form of VM_DEAD and handle concurrent and conflicting address space operations. -- Michal Hocko SUSE Labs