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=-5.8 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 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 96886C433E6 for ; Tue, 9 Feb 2021 09:07:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A3A864EC5 for ; Tue, 9 Feb 2021 09:07:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230295AbhBIJCl (ORCPT ); Tue, 9 Feb 2021 04:02:41 -0500 Received: from mx2.suse.de ([195.135.220.15]:36146 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230286AbhBIJAT (ORCPT ); Tue, 9 Feb 2021 04:00:19 -0500 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=1612861172; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qKmPZ6awqg5hjlBR0sI2r8zXB8YBdpf3Fstd9lWw2l4=; b=p4niOOYBVsAxuZvLvSyfuqafhhIwTbqalQ0XUlb0o+XPLT9GQJWEuScror9bMiRAM/VDNR Gg1qoKrVPkiLaebs0ekDczrIK91xZLqc+rSpU+PO8Uxxh1llnmK79t7ldLJZVcdfnC2J7E dBwPdj8xY5v0EllSgVlDCcSTDxSJc8Y= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 14A0BAB71; Tue, 9 Feb 2021 08:59:32 +0000 (UTC) Date: Tue, 9 Feb 2021 09:59:31 +0100 From: Michal Hocko To: David Hildenbrand Cc: Mike Rapoport , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org Subject: Re: [PATCH v17 00/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: References: <20210208211326.GV242749@kernel.org> <1F6A73CF-158A-4261-AA6C-1F5C77F4F326@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1F6A73CF-158A-4261-AA6C-1F5C77F4F326@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon 08-02-21 22:38:03, David Hildenbrand wrote: > > > Am 08.02.2021 um 22:13 schrieb Mike Rapoport : > > > > On Mon, Feb 08, 2021 at 10:27:18AM +0100, David Hildenbrand wrote: > >> On 08.02.21 09:49, Mike Rapoport wrote: > >> > >> Some questions (and request to document the answers) as we now allow to have > >> unmovable allocations all over the place and I don't see a single comment > >> regarding that in the cover letter: > >> > >> 1. How will the issue of plenty of unmovable allocations for user space be > >> tackled in the future? > >> > >> 2. How has this issue been documented? E.g., interaction with ZONE_MOVABLE > >> and CMA, alloc_conig_range()/alloc_contig_pages?. > > > > Secretmem sets the mappings gfp mask to GFP_HIGHUSER, so it does not > > allocate movable pages at the first place. > > That is not the point. Secretmem cannot go on CMA / ZONE_MOVABLE > memory and behaves like long-term pinnings in that sense. This is a > real issue when using a lot of sectremem. A lot of unevictable memory is a concern regardless of CMA/ZONE_MOVABLE. As I've said it is quite easy to land at the similar situation even with tmpfs/MAP_ANON|MAP_SHARED on swapless system. Neither of the two is really uncommon. It would be even worse that those would be allowed to consume both CMA/ZONE_MOVABLE. One has to be very careful when relying on CMA or movable zones. This is definitely worth a comment in the kernel command line parameter documentation. But this is not a new problem. -- Michal Hocko SUSE Labs