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=-2.2 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 07431C6778D for ; Wed, 12 Sep 2018 16:20:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3AED20880 for ; Wed, 12 Sep 2018 16:20:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B3AED20880 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727843AbeILV0E (ORCPT ); Wed, 12 Sep 2018 17:26:04 -0400 Received: from mx2.suse.de ([195.135.220.15]:36892 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726854AbeILV0E (ORCPT ); Wed, 12 Sep 2018 17:26:04 -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 739E6AF87; Wed, 12 Sep 2018 16:20:47 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B1DB61E3613; Wed, 12 Sep 2018 18:20:46 +0200 (CEST) Date: Wed, 12 Sep 2018 18:20:46 +0200 From: Jan Kara To: "Kani, Toshi" Cc: "jack@suse.cz" , "dan.j.williams@intel.com" , "adilger.kernel@dilger.ca" , "linux-nvdimm@lists.01.org" , "linux-ext4@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "tytso@mit.edu" Subject: Re: [PATCH 1/2] ext4, dax: update dax check to skip journal inode Message-ID: <20180912162046.GA23522@quack2.suse.cz> References: <20180911154246.6844-1-toshi.kani@hpe.com> <20180911154246.6844-2-toshi.kani@hpe.com> <20180912092422.GA7782@quack2.suse.cz> <92faf51ac89e62dcd67e39cc66eef60966d1263c.camel@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <92faf51ac89e62dcd67e39cc66eef60966d1263c.camel@hpe.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 12-09-18 15:47:12, Kani, Toshi wrote: > On Wed, 2018-09-12 at 11:24 +0200, Jan Kara wrote: > > On Tue 11-09-18 09:42:45, Toshi Kani wrote: > > > Ext4 mount path calls ext4_iget() to obtain the journal inode. This > > > inode does not support DAX, and 'ext4_da_aops' needs to be set. It > > > currently works for the DAX mount case because ext4_iget() always set > > > 'ext4_da_aops' to any regular files. > > > > > > ext4_fill_super > > > ext4_load_journal > > > ext4_get_journal_inode > > > ext4_iget > > > > > > In preparation to fix ext4_iget() to set 'ext4_dax_aops' for DAX files, > > > update ext4_should_use_dax() to return false for the journal inode. > > > > > > Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086 > > > Signed-off-by: Toshi Kani > > > Cc: Jan Kara > > > Cc: Dan Williams > > > Cc: "Theodore Ts'o" > > > Cc: Andreas Dilger > > > > The journal inode is similar to any other 'system' inode we have in ext4. > > We don't really expect any of the address space operations to be called for > > it because we don't use page cache with these inodes. Very similar > > situation is with e.g. quota files. So to me it seems this patch is not > > really necessary. Or did you observe any bad effects without this patch? > > Yes, without this change, mount fails with the error below. I believe > .bmap operation in ext4_da_aops is necessary for this case. > > jbd2_journal_init_inode: Cannot locate journal superblock > EXT4-fs > (pmem1): Could not load journal inode Ah, OK, forgot about this. Then how about adding: .bmap = ext4_bmap, to ext4_dax_aops? .bmap is completely fine for DAX inodes and there's no reason to disallow it. Honza -- Jan Kara SUSE Labs, CR