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 B852AC433E6 for ; Thu, 28 Jan 2021 13:50:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A90164DD8 for ; Thu, 28 Jan 2021 13:50:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231252AbhA1NuZ (ORCPT ); Thu, 28 Jan 2021 08:50:25 -0500 Received: from mx2.suse.de ([195.135.220.15]:37626 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229811AbhA1NuW (ORCPT ); Thu, 28 Jan 2021 08:50:22 -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=1611841775; h=from:from:reply-to: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=75llh3uw6L6UpTgmVsHlz+i8LHZJ84jNMGnauBZqITc=; b=RFEQmGK/LljkSM2oiWx77CIGoV0eKNOaEQIEAkrhzpN9jbb3MOKURRCYaRwYVt6/w/U/+e g4VVantqh8P7n2dKzYTMYQk4w9MXZKXSASL6hjd+n4xFytPepUsla6MMacf9DtnSP1AmZ/ v2BcnFvMM+kSY0c0Ye3UOYH/R63VQ8Q= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9E752AF78; Thu, 28 Jan 2021 13:49:35 +0000 (UTC) Date: Thu, 28 Jan 2021 14:49:34 +0100 From: Michal Hocko To: Christoph Lameter Cc: Mike Rapoport , David Hildenbrand , Andrew Morton , Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , 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, Hagen Paul Pfeifer , Palmer Dabbelt Subject: Re: [PATCH v16 07/11] secretmem: use PMD-size pages to amortize direct map fragmentation Message-ID: References: <20210121122723.3446-1-rppt@kernel.org> <20210121122723.3446-8-rppt@kernel.org> <20210126114657.GL827@dhcp22.suse.cz> <303f348d-e494-e386-d1f5-14505b5da254@redhat.com> <20210126120823.GM827@dhcp22.suse.cz> <20210128092259.GB242749@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 28-01-21 13:28:10, Cristopher Lameter wrote: > On Thu, 28 Jan 2021, Michal Hocko wrote: > > > > So, if I understand your concerns correct this implementation has two > > > issues: > > > 1) allocation failure at page fault that causes unrecoverable OOM and > > > 2) a possibility for an unprivileged user to deplete secretmem pool and > > > cause (1) to others > > > > > > I'm not really familiar with OOM internals, but when I simulated an > > > allocation failure in my testing only the allocating process and it's > > > parent were OOM-killed and then the system continued normally. > > > > If you kill the allocating process then yes, it would work, but your > > process might be the very last to be selected. > > OOMs are different if you have a "constrained allocation". In that case it > is the fault of the process who wanted memory with certain conditions. > That memory is not available. General memory is available though. In that > case the allocating process is killed. I do not see this implementation would do anything like that. Neither anything like that implemented in the oom killer. Constrained allocations (cpusets/memcg/mempolicy) only do restrict their selection to processes which belong to the same domain. So I am not really sure what you are referring to. The is only a global knob to _always_ kill the allocating process on OOM. -- Michal Hocko SUSE Labs