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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=unavailable 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 53084C10F00 for ; Wed, 27 Mar 2019 23:31:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 229802087C for ; Wed, 27 Mar 2019 23:31:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727922AbfC0XbX (ORCPT ); Wed, 27 Mar 2019 19:31:23 -0400 Received: from mx2.suse.de ([195.135.220.15]:42780 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725601AbfC0XbX (ORCPT ); Wed, 27 Mar 2019 19:31:23 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 82C98AE25; Wed, 27 Mar 2019 23:31:22 +0000 (UTC) Date: Wed, 27 Mar 2019 18:31:20 -0500 From: Goldwyn Rodrigues To: Matthew Wilcox Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 01/15] btrfs: create a mount option for dax Message-ID: <20190327233120.ykjmdvedr4gsdyhr@merlin> References: <20190326190301.32365-1-rgoldwyn@suse.de> <20190326190301.32365-2-rgoldwyn@suse.de> <20190326191001.GP10344@bombadil.infradead.org> <20190327110052.pvn5dag2xwy2tnkv@merlin> <20190327120031.GR10344@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190327120031.GR10344@bombadil.infradead.org> User-Agent: NeoMutt/20180323 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 5:00 27/03, Matthew Wilcox wrote: > On Wed, Mar 27, 2019 at 06:00:52AM -0500, Goldwyn Rodrigues wrote: > > On 12:10 26/03, Matthew Wilcox wrote: > > > On Tue, Mar 26, 2019 at 02:02:47PM -0500, Goldwyn Rodrigues wrote: > > > > This sets S_DAX in inode->i_flags, which can be used with > > > > IS_DAX(). > > > > > > > > The dax option is restricted to non multi-device mounts. > > > > dax interacts with the device directly instead of using bio, so > > > > all bio-hooks which we use for multi-device cannot be performed > > > > here. While regular read/writes could be manipulated with > > > > RAID0/1, mmap() is still an issue. > > > > > > > > Auto-setting free space tree, because dealing with free space > > > > inode (specifically readpages) is a nightmare. > > > > Auto-setting nodatasum because we don't get callback for writing > > > > checksums after mmap()s. > > > > > > Congratulations on getting the bear to dance. But why? > > > > Why not ? ;) > > 18 files changed, 662 insertions(+), 77 deletions(-) > > I want to know what advantage we're getting for that. So the prime advantages are btrfs filesystem snapshots on the dax device. Leveraging btrfs features, reflinks works just as well. (In addition to all the advantages dax has to offer) -- Goldwyn