From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id D28746B0269 for ; Wed, 27 Jun 2018 03:54:05 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id j11-v6so1069372edr.15 for ; Wed, 27 Jun 2018 00:54:05 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id g18-v6si1780179edh.52.2018.06.27.00.54.04 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 27 Jun 2018 00:54:04 -0700 (PDT) Date: Wed, 27 Jun 2018 09:54:03 +0200 From: Michal Hocko 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: Sender: owner-linux-mm@kvack.org List-ID: 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 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