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=-18.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2A52CC4338F for ; Tue, 27 Jul 2021 09:48:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 090DD61266 for ; Tue, 27 Jul 2021 09:48:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236064AbhG0JsM (ORCPT ); Tue, 27 Jul 2021 05:48:12 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:23908 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236061AbhG0JsL (ORCPT ); Tue, 27 Jul 2021 05:48:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1627379291; h=from:from:reply-to:subject:subject: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=lcHYy4rfAcV2BB+JWTtejLxqwQCZQnvr/lBGXuRnna0=; b=NjSNlINiuMFr/Z9u2lDAN+76rmLcFucfsLniDFUv3Bojt2a195W7EOWW/qSOoPoHmJRRDL 70jjAjE+R5MoP9frs9s6IGhcabmbk8NbupiHo+8fFIhPK9AcRlKBrl5uYKzWt2KV3ap7YE bVhEKtII9TygHwS7IwgI3QqrrVhei/w= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-179-M1Je2zwdODmaFmwX7wZkUQ-1; Tue, 27 Jul 2021 05:48:10 -0400 X-MC-Unique: M1Je2zwdODmaFmwX7wZkUQ-1 Received: by mail-wm1-f70.google.com with SMTP id n10-20020a05600c4f8ab029024eabacb065so846073wmq.2 for ; Tue, 27 Jul 2021 02:48:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:organization:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=lcHYy4rfAcV2BB+JWTtejLxqwQCZQnvr/lBGXuRnna0=; b=YS+v4HobZUlIBPZMh3KvprWtEmj7y8/hyzwt3/LJ/Nj5rfhInJ3SsLtHOW0dH4TTji omJc+9WKTgt+SRAnd/hbkehMwtb3GH9Iu/sE/0z1uq62OE7WyjWICzjc+Yi66Y1H2b5M YKWFoMwrcEPS91d8vnkOg28qka52OfxJ2TPBsKdvfT8gY11Z8wZsw3Ea1AS4qVJe/yTF RcIdGmfbItQ1Ouo0c9NTO+8vKQOV+IyuqXyZyLlIVD5M/spq9pEK0rTujsjQl28zBtYS uuv4Xt+82SMmUnNL0OBpqHTH5X3kTt3ObFiQt1RbfN4nSHhJHN+TaYYVAAvZJnYRPpmR RCVg== X-Gm-Message-State: AOAM532qKm7bdBfdHITCRNDHwFBkjZJLtM6Ji2Vka1kNMsrqYyiJI9oF FcrQ18PNsefV9MiD/hyyvTTRHhNXq0f6p6PXZ4NGx9JLamxDdD/2uAl+4+QZzSHveAk1RlqM9j/ IP0GEWfLLVXIvMMr5/s1c X-Received: by 2002:adf:fbce:: with SMTP id d14mr23630128wrs.236.1627379288825; Tue, 27 Jul 2021 02:48:08 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyW+5bsug3BLc5GikuPVa91Lj121RhsP8kBvehx197gg7taI+A14JR9q78R+cw9t8XabRPdHg== X-Received: by 2002:adf:fbce:: with SMTP id d14mr23630096wrs.236.1627379288633; Tue, 27 Jul 2021 02:48:08 -0700 (PDT) Received: from [192.168.3.132] (p4ff23c36.dip0.t-ipconnect.de. [79.242.60.54]) by smtp.gmail.com with ESMTPSA id e3sm2719905wrw.51.2021.07.27.02.48.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Jul 2021 02:48:08 -0700 (PDT) To: Evan Green , Andrew Morton Cc: Michal Hocko , Pavel Machek , linux-api@vger.kernel.org, Alex Shi , Alistair Popple , Johannes Weiner , Joonsoo Kim , "Matthew Wilcox (Oracle)" , Miaohe Lin , Minchan Kim , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210726171106.v4.1.I09866d90c6de14f21223a03e9e6a31f8a02ecbaf@changeid> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v4] mm: Enable suspend-only swap spaces Message-ID: Date: Tue, 27 Jul 2021 11:48:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210726171106.v4.1.I09866d90c6de14f21223a03e9e6a31f8a02ecbaf@changeid> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 27.07.21 02:12, Evan Green wrote: > Add a new SWAP_FLAG_HIBERNATE_ONLY that adds a swap region but refuses > to allow generic swapping to it. This region can still be wired up for > use in suspend-to-disk activities, but will never have regular pages > swapped to it. This flag will be passed in by utilities like swapon(8), > usage would probably look something like: swapon -o hibernate /dev/sda2. > > Currently it's not possible to enable hibernation without also enabling > generic swap for a given area. One semi-workaround for this is to delay > the call to swapon() until just before attempting to hibernate, and then > call swapoff() just after hibernate completes. This is somewhat kludgy, > and also doesn't really work to keep swap out of the hibernate region. > When hibernate begins, it starts by allocating a large chunk of memory > for itself. This often ends up forcing a lot of data out into swap. By > this time the hibernate region is eligible for generic swap, so swap > ends up leaking into the hibernate region even with the workaround. > > There are a few reasons why usermode might want to be able to > exclusively steer swap and hibernate. One reason relates to SSD wearing. > Hibernate's endurance and speed requirements are different from swap. > It may for instance be advantageous to keep hibernate in primary > storage, but put swap in an SLC namespace. These namespaces are faster > and have better endurance, but cost 3-4x in terms of capacity. > Exclusively steering hibernate and swap enables system designers to > accurately partition their storage without either wearing out their > primary storage, or overprovisioning their fast swap area. > > Another reason to allow exclusive steering has to do with security. > The requirements for designing systems with resilience against > offline attacks are different between swap and hibernate. Swap > effectively requires a dictionary of hashes, as pages can be added and > removed arbitrarily, whereas hibernate only needs a single hash for the > entire image. If you've set up block-level integrity for swap and > image-level integrity for hibernate, then allowing swap blocks to > possibly leak out to the hibernate region is problematic, since it > creates swap pages not protected by any integrity. > > Swap regions with SWAP_FLAG_HIBERNATE_ONLY set will not appear in > /proc/meminfo under SwapTotal and SwapFree, since they are not usable as > general swap. These regions do still appear in /proc/swaps. Right, and they also don't account towards the memory overcommit calculations. Thanks for extending the patch description! [...] > + if (swap_flags & SWAP_FLAG_HIBERNATE_ONLY) { > + if (IS_ENABLED(CONFIG_HIBERNATION)) { > + if (swap_flags & ~SWAP_HIBERNATE_ONLY_VALID_FLAGS) > + return -EINVAL; > + > + } else { > + return -EINVAL; > + } > + } We could do short if ((swap_flags & SWAP_FLAG_HIBERNATE_ONLY) && (!IS_ENABLED(CONFIG_HIBERNATION) || (swap_flags & ~SWAP_HIBERNATE_ONLY_VALID_FLAGS))) return -EINVAL; or if (swap_flags & SWAP_FLAG_HIBERNATE_ONLY)) if (!IS_ENABLED(CONFIG_HIBERNATION) || (swap_flags & ~SWAP_HIBERNATE_ONLY_VALID_FLAGS)) return -EINVAL; > + > if (!capable(CAP_SYS_ADMIN)) > return -EPERM; > > @@ -3335,16 +3366,20 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > if (swap_flags & SWAP_FLAG_PREFER) > prio = > (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; > + > + if (swap_flags & SWAP_FLAG_HIBERNATE_ONLY) > + p->flags |= SWP_HIBERNATE_ONLY; > enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map); > > - pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n", > + pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s%s\n", > p->pages<<(PAGE_SHIFT-10), name->name, p->prio, > nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), > (p->flags & SWP_SOLIDSTATE) ? "SS" : "", > (p->flags & SWP_DISCARDABLE) ? "D" : "", > (p->flags & SWP_AREA_DISCARD) ? "s" : "", > (p->flags & SWP_PAGE_DISCARD) ? "c" : "", > - (frontswap_map) ? "FS" : ""); > + (frontswap_map) ? "FS" : "", > + (p->flags & SWP_HIBERNATE_ONLY) ? "H" : ""); > > mutex_unlock(&swapon_mutex); > atomic_inc(&proc_poll_event); > Looks like the cleanest alternative to me, as long as we don't want to invent new interfaces. Acked-by: David Hildenbrand -- Thanks, David / dhildenb