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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 65B7BC433DF for ; Fri, 16 Oct 2020 13:15:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BEB4820848 for ; Fri, 16 Oct 2020 13:15:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="GnUJU6yo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407065AbgJPNPd (ORCPT ); Fri, 16 Oct 2020 09:15:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:44826 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404838AbgJPNPd (ORCPT ); Fri, 16 Oct 2020 09:15:33 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1602854132; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=bvAhj5rd9TdNJeHXm3trKOnA1tBOciYDggMWpj0b74s=; b=GnUJU6yoCfhaA7heEo3YN761vM6a4v/S6AoyAIUE1JTIq02xvo/izHii3S2UTgT0IyAGSj j2DdI+fdP0DEYOd7uNGqxuGV6FGDok/QyT2llMJ0mGTHRAoNJwi7Zw03VsE8o0WsrjGiRy 1Uarp2X6M62vtyAO7wXG7DdBrs4uU4Q= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 6FE7CAB0E; Fri, 16 Oct 2020 13:15:32 +0000 (UTC) Date: Fri, 16 Oct 2020 15:15:31 +0200 From: Michal Hocko To: osalvador@suse.de Cc: Shijie Luo , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linmiaohe@huawei.com, linfeilong@huawei.com Subject: Re: [PATCH] mm: fix potential pte_unmap_unlock pte error Message-ID: <20201016131531.GK22589@dhcp22.suse.cz> References: <20201015121534.50910-1-luoshijie1@huawei.com> <20201016123137.GH22589@dhcp22.suse.cz> <20201016131112.GJ22589@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201016131112.GJ22589@dhcp22.suse.cz> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 16-10-20 15:11:17, Michal Hocko wrote: > On Fri 16-10-20 14:37:08, osalvador@suse.de wrote: > > On 2020-10-16 14:31, Michal Hocko wrote: > > > I do not like the fix though. The code is really confusing. Why should > > > we check for flags in each iteration of the loop when it cannot change? > > > Also why should we take the ptl lock in the first place when the look is > > > broken out immediately? > > > > About checking the flags: > > > > https://lore.kernel.org/linux-mm/20190320081643.3c4m5tec5vx653sn@d104.suse.de/#t > > This didn't really help. Maybe the code was different back then but > right now the code doesn't make much sense TBH. The only reason to check > inside the loop would be to have a completely unpopulated address range. > Note about MPOL_MF_STRICT is not checked explicitly and I do not see how > it makes any difference. Ohh, I have missed queue_pages_required. Let me think some more. -- Michal Hocko SUSE Labs