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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 01E40C43219 for ; Thu, 2 May 2019 01:52:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AA6C8206DF for ; Thu, 2 May 2019 01:52:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="e1Cdnr7M" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AA6C8206DF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 44DAA6B0005; Wed, 1 May 2019 21:52:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3D7F36B0006; Wed, 1 May 2019 21:52:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 251126B0007; Wed, 1 May 2019 21:52:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-pg1-f197.google.com (mail-pg1-f197.google.com [209.85.215.197]) by kanga.kvack.org (Postfix) with ESMTP id DD5106B0005 for ; Wed, 1 May 2019 21:52:17 -0400 (EDT) Received: by mail-pg1-f197.google.com with SMTP id e12so461587pgh.2 for ; Wed, 01 May 2019 18:52:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:date:from:to:cc:subject :message-id:references:mime-version:content-disposition:in-reply-to :user-agent; bh=xNjOP9gg2QMy4x3ICBZoOoeoO4NbjsoS8XWQ33F0y5I=; b=uhwEEIs8pNE9T35AuH2gPcphp3othwbc/EIB7LD2J6RfV+m/39384s8c34Z5gceE7N ws0X49KEd+xbRHHgmA3jUZlyFnQmySdsKyInS7YrCalS3duE/MZfruibDYUSbtTNHn71 SFLgpJrwVAVQklAgfamkUQSo1V19LW8/VBSdXPEtPyLjj3nfed7EAyqSn53w5YflntYK gNrtxR95zPqEv7Vf6UIP43dMnwbr6Pk1GkyCBgLEjVRsKbbbigRem0lcp8GynbB0v3+1 egYaV5eMjqyWIpW0zyYO/1Ycahj6qc4r1NShk9Sqi8ORoMwZLgRtYPF06+T40LRDyHTh zIrw== X-Gm-Message-State: APjAAAWApXmE40O/A4MEKYyt9+pe6a8no6BLt04nr5tw1gPBJrYcf4eM SIajMKOBTTogwzlg9yjiq3+WUgbPLtWdlbDpIhXm2WJp8iZ+DQaTkJWXKicwDsKX7YjV/34Ffgd 5Hr4TE998HaRJDUti8MBMZOEkbp4yf/CeWLI3KFBu7WA8wNxgEHR4S0GN9rnW2VI8Sg== X-Received: by 2002:a17:902:324:: with SMTP id 33mr845781pld.246.1556761937566; Wed, 01 May 2019 18:52:17 -0700 (PDT) X-Google-Smtp-Source: APXvYqyZdjF2JrVG3PU5DEBSCTboOFnL+eJvo7ZoRnPuSHWrBu+kHsB9bet+8tWnHMxsk7lT6xWQ X-Received: by 2002:a17:902:324:: with SMTP id 33mr845734pld.246.1556761936763; Wed, 01 May 2019 18:52:16 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1556761936; cv=none; d=google.com; s=arc-20160816; b=tTXbU0c0a2u9jtkUSchBLjVXDGA6zbh9v2tnpkakkSCmNbU5A4/mLZEm30IHZn12C5 guWDavP7aV2pcaXLzaaHqzA5ojQoYYpwYmdMrU3DXEe6VqH7pc7JnvLZnKMygFpYTa2S +UYvw1vg2yM4ouzntdSwsAAUcjzdbLMCiHIJZdpjw9EuDPWCcg3hLjvDOvaKofXows1z afyPzZeeEyMsYoasTPtMvBO0IgAps7qvxwBOXOajmBsmHQBfqw6vQ1k+jRXGaS85YPcC BAvzpBOBYaPY7JEAdtwOvyH3nXbXZHaElxJVHpjOcK2360vEqklM4z/uz+koufiE683E aIYA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature; bh=xNjOP9gg2QMy4x3ICBZoOoeoO4NbjsoS8XWQ33F0y5I=; b=HLGQMWgrlTRV1wNLk3pIv9INK14T+l8HT5w/iaAltJaNxt/rduEEFusDjnPsr1XIz1 m0rglsH2zqQ8KPAHu9S3niTJ6A1KKKAdYCitKo6VX+UJBMG7EEFClUtAyankC5K+8WUK nHn/p6BfMOpP5qpkAB7sp5Fpo5qUktdhRsmOcl9FrHrUvcvws48iszwH3zqd4epvde3B Kzm92Rf6UMpEKyR9jxDzbs62HTOTqgZ8POYqqz4KX/5VjWHpGLWqAd5EhgegPpL024nf r6EoiVuzL+fk8FGlhYsWaOUj0HLLizeweJk316+UvhwCwCEwygPjHcT0wig0O/3wyL3B MRoQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=e1Cdnr7M; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133]) by mx.google.com with ESMTPS id 35si35559944ple.382.2019.05.01.18.52.16 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 01 May 2019 18:52:16 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=e1Cdnr7M; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=xNjOP9gg2QMy4x3ICBZoOoeoO4NbjsoS8XWQ33F0y5I=; b=e1Cdnr7Mt+nZArvTOHcIt/dcH Ie+TXMWhFAYA5HNxT+y63lHRcgthMLNLL/PSs84r2uhvCLp73HMv7fZ+6i58oeYNTdQzpVsYqdBF3 nSsIM/r501mqjtAIkshkaSAWXLi3+lfbyh811CpB3RgxxHaVYJa6loRHloXhQ1iJ/dbbmb3AJHj1t pj+KBXXwUGZS7zTl5dGTlNJJTY1q4Id6eY+DUeLIZg2fShSdrsNHDR9dS/jmOXHnDsJZoKQLz3Qn1 j4DV7gXZmiWBaXasQ1mnVROZhkNd7/lbqMTeCiyj5EpOonGLtzfwRwoMya+eznp6sO5aOwOgMiYnW PWVOs2XIQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1hM0tT-0005DI-4W; Thu, 02 May 2019 01:52:15 +0000 Date: Wed, 1 May 2019 18:52:14 -0700 From: Matthew Wilcox To: Jerome Glisse Cc: Dave Chinner , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [LSF/MM TOPIC] Direct block mapping through fs for device Message-ID: <20190502015214.GB8099@bombadil.infradead.org> References: <20190426013814.GB3350@redhat.com> <20190426062816.GG1454@dread.disaster.area> <20190426152044.GB13360@redhat.com> <20190427012516.GH1454@dread.disaster.area> <20190429132643.GB3036@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190429132643.GB3036@redhat.com> User-Agent: Mutt/1.9.2 (2017-12-15) 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 Mon, Apr 29, 2019 at 09:26:45AM -0400, Jerome Glisse wrote: > This is a filesystem opt-in feature if a given filesystem do not want > to implement it then just do not implement it and it will use page > cache. It is not mandatory i am not forcing anyone. The first reasons > for those are not filesystem but mmap of device file. But as LSF/MM > is up i thought it would be a good time to maybe propose that for file- > system too. If you do not want that for your filesystem then just NAK > any patch that add that to filesystem you care about. No. This is stupid, broken, and wrong. I know we already have application-visible differences between filesystems, and every single one of those is a bug. They may be hard bugs to fix, they may be bugs that we feel like we can't fix, they may never be fixed. But they are all bugs. Applications should be able to work on any Linux filesystem without having to care what it is. Code has a tendency to far outlive its authors expectations (and indeed sometimes its authors). If 'tar' had an #ifdef XFS / #elsif EXT4 / #elsif BTRFS / ... #endif, that would be awful. We need the same semantics across all major filesystems. Anything else is us making application developers lives harder than necessary, and that's unacceptable.