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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,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 318AFC43381 for ; Thu, 28 Mar 2019 17:27:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 09B572173C for ; Thu, 28 Mar 2019 17:27:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726076AbfC1R1Q (ORCPT ); Thu, 28 Mar 2019 13:27:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:39754 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725816AbfC1R1P (ORCPT ); Thu, 28 Mar 2019 13:27:15 -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 821BEAB98; Thu, 28 Mar 2019 17:27:14 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 4EC00DA911; Thu, 28 Mar 2019 18:28:25 +0100 (CET) Date: Thu, 28 Mar 2019 18:28:25 +0100 From: David Sterba To: Goldwyn Rodrigues Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Goldwyn Rodrigues Subject: Re: [PATCH 01/15] btrfs: create a mount option for dax Message-ID: <20190328172825.GQ29086@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Goldwyn Rodrigues , linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Goldwyn Rodrigues References: <20190326190301.32365-1-rgoldwyn@suse.de> <20190326190301.32365-2-rgoldwyn@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190326190301.32365-2-rgoldwyn@suse.de> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Tue, Mar 26, 2019 at 02:02:47PM -0500, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues > > 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. I'm looking for other features that would not work with dax. Disabling multiple devices strikes out device add, device delete and device replace. To be verified: - balance - at least profile changes must be forbidden - defrag - compression - as it needs COW, it won't work on the nodatacow files, thus seems to be ok - resize/grow - this could work without changes, no block relocation is needed, only new structures created - resize/shrink - depends on balance, the block groups from the removed area need to be relocated - swapfiles - I'm sure somebody will try that; I haven't seen any IS_DAX checks in the swapfile activation code