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 7FFF0C43333 for ; Wed, 10 Mar 2021 13:03:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6902264FF3 for ; Wed, 10 Mar 2021 13:03:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231916AbhCJNDD (ORCPT ); Wed, 10 Mar 2021 08:03:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41286 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229660AbhCJNCe (ORCPT ); Wed, 10 Mar 2021 08:02:34 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF6AEC061760; Wed, 10 Mar 2021 05:02:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=ALr5iWDNLGdU3HVoDSzUHGSO+jgvXP9RVBf6+KXFgYU=; b=G03GxTkrZ0HvyN9TVTTGv9fFLu gglr3sTaBNVnfJtIdTSSB3LxjkuAQCN2m8iNAGscB85rKFvB+BNOo0fcOeMhm6uSOC32XSEbiHq8C pqA92+K31BjmkI5VQ4CKOtGV0af3hjaG+wyN5nnEIbT1f4dhM5s114qtLSudoKjXcF4vjuLaUUQuW PBedOIBQUD58iR43kVmEiEOTxom08dYlGj2BYh9vMwA+ltYAI5zuIhaV6NSnijO6ClL59uCl0bJTl iwWyJUrreoI1HR6Nn9PaGnXWN98KC9HTZzq/VQTuGCX7GPBlPOIRxLVlfNfcjMjnM+7KQ62pgaidJ hsNHYh/Q==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lJyTr-003TrT-Va; Wed, 10 Mar 2021 13:02:28 +0000 Date: Wed, 10 Mar 2021 13:02:27 +0000 From: Matthew Wilcox To: Neal Gompa Cc: Shiyang Ruan , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel , darrick.wong@oracle.com, dan.j.williams@intel.com, jack@suse.cz, viro@zeniv.linux.org.uk, Btrfs BTRFS , ocfs2-devel@oss.oracle.com, david@fromorbit.com, hch@lst.de, rgoldwyn@suse.de Subject: Re: [PATCH v2 00/10] fsdax,xfs: Add reflink&dedupe support for fsdax Message-ID: <20210310130227.GN3479805@casper.infradead.org> References: <20210226002030.653855-1-ruansy.fnst@fujitsu.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-fsdevel@vger.kernel.org On Wed, Mar 10, 2021 at 07:30:41AM -0500, Neal Gompa wrote: > Forgive my ignorance, but is there a reason why this isn't wired up to > Btrfs at the same time? It seems weird to me that adding a feature btrfs doesn't support DAX. only ext2, ext4, XFS and FUSE have DAX support. If you think about it, btrfs and DAX are diametrically opposite things. DAX is about giving raw access to the hardware. btrfs is about offering extra value (RAID, checksums, ...), none of which can be done if the filesystem isn't in the read/write path. That's why there's no DAX support in btrfs. If you want DAX, you have to give up all the features you like in btrfs. So you may as well use a different filesystem.