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 C23CFC43144 for ; Wed, 27 Jun 2018 07:54:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6FD1F264C6 for ; Wed, 27 Jun 2018 07:54:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6FD1F264C6 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 S1753209AbeF0HyG (ORCPT ); Wed, 27 Jun 2018 03:54:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:43171 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752364AbeF0HyF (ORCPT ); Wed, 27 Jun 2018 03:54:05 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext-too.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 4C50CAAF3; Wed, 27 Jun 2018 07:54:04 +0000 (UTC) Date: Wed, 27 Jun 2018 09:54:03 +0200 From: Michal Hocko To: Vlastimil Babka Cc: Andrew Morton , JianKang Chen , Mel Gorman , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, xieyisheng1@huawei.com, guohanjun@huawei.com, wangkefeng.wang@huawei.com Subject: Re: [PATCH] mm: drop VM_BUG_ON from __get_free_pages Message-ID: <20180627075403.GG32348@dhcp22.suse.cz> References: <20180622162841.25114-1-mhocko@kernel.org> <6886dee0-3ac4-ef5d-3597-073196c81d88@suse.cz> <20180626100416.a3ff53f5c4aac9fae954e3f6@linux-foundation.org> <20180627073420.GD32348@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Wed 27-06-18 09:50:01, Vlastimil Babka wrote: > On 06/27/2018 09:34 AM, Michal Hocko wrote: > > On Tue 26-06-18 10:04:16, Andrew Morton wrote: > > > > And as I've argued before the code would be wrong regardless. We would > > leak the memory or worse touch somebody's else kmap without knowing > > that. So we have a choice between a mem leak, data corruption k or a > > silent fixup. I would prefer the last option. And blowing up on a BUG > > is not much better on something that is easily fixable. I am not really > > convinced that & ~__GFP_HIGHMEM is something to lose sleep over. > > Maybe put the fixup into a "#ifdef CONFIG_HIGHMEM" block and then modern > systems won't care? In that case it could even be if (WARN_ON_ONCE(...)) > so future cases with wrong expectations would become known. Yes that could be done as well. Or maybe we can make __GFP_HIGHMEM 0 for !HIGHMEM systems. Does something really rely on it being non-zero? -- Michal Hocko SUSE Labs