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=-6.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 208DDC433DB for ; Thu, 11 Feb 2021 11:56:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD27964DA5 for ; Thu, 11 Feb 2021 11:56:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229999AbhBKLzj (ORCPT ); Thu, 11 Feb 2021 06:55:39 -0500 Received: from mail.kernel.org ([198.145.29.99]:42090 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231628AbhBKLap (ORCPT ); Thu, 11 Feb 2021 06:30:45 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2C89C601FF; Thu, 11 Feb 2021 11:29:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613043004; bh=JtJHuqvnhxNyM0cSP3Qe3tSMfjdJGVz3S+tERJXfo4M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PEXygoi6R9pVpb0NPj47+Ko3f1Ah21CxDjueYWnlQAO/uRVErOda0UIyi9V6v9rYs 6NXsauRjapfptBwBvo70ls3AAnv08VDhhWUxi7yLuKhQOTQa31mGOOLAdVpQ8B16uZ SzyBJMAmkReTwWmxT4Tjvg8ZAL2HyRIawjk70IsH5WPDvqJ9dQdETycAuzkDATgNju gOL/aozy2VFMdzBaSlauwv+UBb82EKAQG3vL++P2TTqj9pWtgKqRk4VcEXI1wyFYG+ 5DJMf90zHF2E2ie9ZUU2VlL1vbBwnzXXk30WzSnRm7nZHI33uXE/tbEgH+TreMHc5x BblQZ8rwiMN2Q== Date: Thu, 11 Feb 2021 13:29:46 +0200 From: Mike Rapoport To: David Hildenbrand Cc: Michal Hocko , 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 , 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 v17 07/10] mm: introduce memfd_secret system call to create "secret" memory areas Message-ID: <20210211112946.GJ242749@kernel.org> References: <20210208212605.GX242749@kernel.org> <20210209090938.GP299309@linux.ibm.com> <20210211071319.GF242749@kernel.org> <0d66baec-1898-987b-7eaf-68a015c027ff@redhat.com> 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, Feb 11, 2021 at 11:02:07AM +0100, David Hildenbrand wrote: > > Another thought regarding "doesn't have _any_ backing storage" > > What are the right semantics when it comes to memory accounting/commit? > > As secretmem does not have > a) any backing storage > b) cannot go to swap > > The MAP_NORESERVE vs. !MAP_NORESERVE handling gets a little unclear. Why > "reserve swap space" if the allocations cannot ever go to swap? Sure, we > want to "reserve physical memory", but in contrast to other users that can > go to swap. > > Of course, this is only relevant for MAP_PRIVATE secretmem mappings. Other > MAP_SHARED assumes there is no need for reserving swap space as it can just > go to the backing storage. (yeah, tmpfs/shmem is weird in that regard as > well, but again, it's a bit different) In that sense seceremem is as weird as tmpfs and it only allows MAP_SHARED. -- Sincerely yours, Mike.