From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from g9t5009.houston.hpe.com (g9t5009.houston.hpe.com [15.241.48.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 419492112B1D8 for ; Wed, 12 Sep 2018 08:47:16 -0700 (PDT) From: "Kani, Toshi" Subject: Re: [PATCH 1/2] ext4, dax: update dax check to skip journal inode Date: Wed, 12 Sep 2018 15:47:12 +0000 Message-ID: <92faf51ac89e62dcd67e39cc66eef60966d1263c.camel@hpe.com> References: <20180911154246.6844-1-toshi.kani@hpe.com> <20180911154246.6844-2-toshi.kani@hpe.com> <20180912092422.GA7782@quack2.suse.cz> In-Reply-To: <20180912092422.GA7782@quack2.suse.cz> Content-Language: en-US Content-ID: MIME-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: "jack@suse.cz" Cc: "tytso@mit.edu" , "linux-nvdimm@lists.01.org" , "linux-kernel@vger.kernel.org" , "adilger.kernel@dilger.ca" , "linux-ext4@vger.kernel.org" List-ID: 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 > That being said I agree that it would be a good cleanup to define something > like ext4_is_system_inode() and disable DAX for these inodes just because > they are special. But I don't see a need for this as a part of your fix. Is there other system inode we need to check for? Thanks, -Toshi _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm