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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54FF9C61DA4 for ; Thu, 23 Feb 2023 12:26:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A4E116B0072; Thu, 23 Feb 2023 07:26:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9FEB86B0073; Thu, 23 Feb 2023 07:26:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8C8716B0074; Thu, 23 Feb 2023 07:26:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 7F2736B0072 for ; Thu, 23 Feb 2023 07:26:44 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 3BD758073F for ; Thu, 23 Feb 2023 12:26:44 +0000 (UTC) X-FDA: 80498480328.02.D4A81E8 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf14.hostedemail.com (Postfix) with ESMTP id 7ED7C10000B for ; Thu, 23 Feb 2023 12:26:41 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="J3/9vJXx"; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf14.hostedemail.com: domain of brauner@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=brauner@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1677155201; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=EeNeY0a9izKSLLILmZCYMahKVImisW4GrZ4p8ANidmE=; b=5ohhRajDKXyqZbVyp36MgsePMQUyghO8MGgf6hBqc4tjivcxITUmqBwuW3iWhEJSahgvTy y0m6D839BY9v52alMl3BNHCkQyE3VGU1usi9X4naIw7WrvrqccRWbGgoInM2Pys4Wp3MF5 UOJAZOHzwIzFp/sBbXpxF50sxT3tUFw= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="J3/9vJXx"; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf14.hostedemail.com: domain of brauner@kernel.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=brauner@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1677155201; a=rsa-sha256; cv=none; b=HY5g0+ifn8Ym3DXNdXNVSfY6ipBwoWSGzUV/3Xq4ST5xHWViAZXUiUTHS2xFPgT/ZQmU73 hZj24/omvbOjxcH1+YF7HCCRYAq4xa2EViHwi3VEF8nOGfCoWTRvicmlRtZQjlWvvh5BpW GB73RxMIXyQNntEw4hhnNh+TYzQIA+E= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 5D587B81980; Thu, 23 Feb 2023 12:26:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2ABDEC433EF; Thu, 23 Feb 2023 12:26:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677155198; bh=dqlSVxQZeCY+YaNwcYKBewFsr2tm4s6bQA68OMlnzPc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=J3/9vJXxfJa1SR+quJoOh5+BE39nMvrNHyQDhav7wt0ssK7n5kTCfWqwdeWoi/tNK wPIMQWiQlg0PepmBQv/cEPr/PWu4EppQolUIoQ9wXAu4CJtfsGaA7sZKV3MyVGv7EI 8vbMZ+IoOZNSfijEhWjzEK/bX43YpSfqIwTf3KigJNreuJSwvyIeoyJywJM6fQoBSo IUMe8NY5HUjM+L8zau/a2y0x1L6aI60Ciciohk28tC+hK9eBjlVljt+Fj4WXYmWG/l 4IwKPxcd1zK81t0FfLypW3PL0jj8YCiPO4DYQBmaKmQmypddYvZcsq8wW6ttuZZZrs EZRpoGf96a5kA== Date: Thu, 23 Feb 2023 13:26:31 +0100 From: Christian Brauner To: Luis Chamberlain Cc: hughd@google.com, akpm@linux-foundation.org, willy@infradead.org, linux-mm@kvack.org, p.raghav@samsung.com, dave@stgolabs.net, a.manzanares@samsung.com, yosryahmed@google.com, linux-kernel@vger.kernel.org Subject: Re: [RFC v2 5/5] shmem: add support to ignore swap Message-ID: <20230223122631.hwvhbqxadvbm23nb@wittgenstein> References: <20230223024412.3522465-1-mcgrof@kernel.org> <20230223024412.3522465-6-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230223024412.3522465-6-mcgrof@kernel.org> X-Rspamd-Queue-Id: 7ED7C10000B X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: ugzd9ecar71acaw34sgp7kqqspkaz3c8 X-HE-Tag: 1677155201-807829 X-HE-Meta: U2FsdGVkX19Q2WD2EXRMSA/jmtCWdF7RIAhfjVvrgU9JHmw1PRpiUkYqBaQUiRr3Qf76l177D7SWNJZqXSKIGtWRuyKmQnwP3MV1wqKnRV5jdwgLw4KMAgbF4RIHMOTzxSOhKovDKTLrszTRgAp5hbMUt5oeQmjgTWl26tKuzNTE/eHGp6dGXVIUbJJUfNxiiYTaqe2LrNd8Je9F2RxKmgQX+sMJMMRb1DXHjjBu1YGPaRHK9aDZinyaxDMKT5O2fZroLY96uLZpfrfdxQrjCYwXdw2+73JathQGCElk9ytNsmFFEQiFOx76QXysigXAol5lEZ8RlSvhdCVguYcz3pQKI+XJnYkkXuGSDR7hikzqX/oxV6LutQ5KIJBB4YkrAtvegj2Msf9wP5x1oTC6t2U/Pz/L8p+7psxCHBJS51kvKVrQDa3o5yW8gz29AGBCbvXGgx1sd7aCM+ZvsrsJKefW8AT1JDN3VNTYRLslu9hNZvjoHBZ5rnG0/NKuPbZ8FpimcziR71HQfiMa1gy3emNrmnjMjTk5bFSIyP90CT37GQpUSS7xxfSKiY/geeWq0m+tjWRLW5/kylJyrvhb/aZ/x6AEOajAapfoAooBvoO3C+IAIImgbERNWmYLF8q8x5p8qvj7BQNDapRgiikIYMzUTKD1x6PoOpoDTGE2344g9QDgvVCwg4aa144kCLix/G5hMMNhrZmptjDvuV3xwvQpVEwMZXaQBBYBj1Z+Da0BHXhzvK9UwtnI4ol1KflPagEq9MITpU/Nb/SRdEmFqt+m9nDvLSRtkTVeKU3ISOg2FoaHG3O2qFsnNuTcsR8uav7FlJnWj9iKfSm2DpHHcmCBT7HtES8AMcUhyVPcF+p7SwCR7BNflETm8/psB5bRShRIdKtLuZebS+GgUMwsiSPh3mf24R3VegXGfhULnhgLljzX3lO68wVfT23NVTxuC1WGJgR4KnIV0HeVBgN JMb5zB1B o7S9AfSnMk+6WVbsHWxl7KZAsMpBABa3fo7f3z3j702zi3+0FN3Sa3YOBxjHc+aKZcCS1H26pXCpHHp7oDP+rTcQwYDr+E7BLMazGOheDqcEaTPYTrO0C9JvuTe0Xubdjy88mKqYgIFZ88183cYabzVr0ScwJ1SYc+WbvR7GaoGCgiQuKxPbASK0g/QWpZyCphqaCYxTulhhXJaFdjn+Gpa8QHmiaZUwv6tVspbM8Thwte3A4U3KXfYcZ72wDOZg8SSp3+giHOB/bbq43fMDrSOh4I8Fy2UbPLpkEk1Vxs7bnkNK/tFhZpnn3ymS73srbp59PFC2rQyTw/O/yp8g4UC/cz+xBDmLeUEbvOGD4YlG3rwc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Feb 22, 2023 at 06:44:12PM -0800, Luis Chamberlain wrote: > In doing experimentations with shmem having the option to avoid swap > becomes a useful mechanism. One of the *raves* about brd over shmem is > you can avoid swap, but that's not really a good reason to use brd if > we can instead use shmem. Using brd has its own good reasons to exist, > but just because "tmpfs" doesn't let you do that is not a great reason > to avoid it if we can easily add support for it. > > I don't add support for reconfiguring incompatible options, but if > we really wanted to we can add support for that. > > To avoid swap we use mapping_set_unevictable() upon inode creation, > and put a WARN_ON_ONCE() stop-gap on writepages() for reclaim. > > Signed-off-by: Luis Chamberlain > --- We would have use-cases for this in systemd. We currently use ramfs for systemd's credential logic since ramfs is unswappable. It'd be very neat if we could use tmpfs instead, Acked-by: Christian Brauner