From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752870AbcBKMub (ORCPT ); Thu, 11 Feb 2016 07:50:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:52518 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752236AbcBKMu3 (ORCPT ); Thu, 11 Feb 2016 07:50:29 -0500 Date: Thu, 11 Feb 2016 13:50:44 +0100 From: Jan Kara To: Ross Zwisler Cc: Dave Chinner , linux-kernel@vger.kernel.org, "Theodore Ts'o" , Alexander Viro , Andreas Dilger , Andrew Morton , Dan Williams , Jan Kara , Matthew Wilcox , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, xfs@oss.sgi.com, Jan Kara Subject: Re: [PATCH v2 2/2] dax: move writeback calls into the filesystems Message-ID: <20160211125044.GJ21760@quack.suse.cz> References: <1455137336-28720-1-git-send-email-ross.zwisler@linux.intel.com> <1455137336-28720-3-git-send-email-ross.zwisler@linux.intel.com> <20160210220312.GP14668@dastard> <20160210224340.GA30938@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160210224340.GA30938@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 10-02-16 15:43:40, Ross Zwisler wrote: > On Thu, Feb 11, 2016 at 09:03:12AM +1100, Dave Chinner wrote: > > On Wed, Feb 10, 2016 at 01:48:56PM -0700, Ross Zwisler wrote: > > > Previously calls to dax_writeback_mapping_range() for all DAX filesystems > > > (ext2, ext4 & xfs) were centralized in filemap_write_and_wait_range(). > > > dax_writeback_mapping_range() needs a struct block_device, and it used to > > > get that from inode->i_sb->s_bdev. This is correct for normal inodes > > > mounted on ext2, ext4 and XFS filesystems, but is incorrect for DAX raw > > > block devices and for XFS real-time files. > > > > > > Instead, call dax_writeback_mapping_range() directly from the filesystem > > > ->writepages function so that it can supply us with a valid block > > > device. This also fixes DAX code to properly flush caches in response to > > > sync(2). > > > > > > Signed-off-by: Ross Zwisler > > > Signed-off-by: Jan Kara > > > --- > > > fs/block_dev.c | 16 +++++++++++++++- > > > fs/dax.c | 13 ++++++++----- > > > fs/ext2/inode.c | 11 +++++++++++ > > > fs/ext4/inode.c | 7 +++++++ > > > fs/xfs/xfs_aops.c | 9 +++++++++ > > > include/linux/dax.h | 6 ++++-- > > > mm/filemap.c | 12 ++++-------- > > > 7 files changed, 58 insertions(+), 16 deletions(-) > > > > > > diff --git a/fs/block_dev.c b/fs/block_dev.c > > > index 39b3a17..fc01e43 100644 > > > --- a/fs/block_dev.c > > > +++ b/fs/block_dev.c > > > @@ -1693,13 +1693,27 @@ static int blkdev_releasepage(struct page *page, gfp_t wait) > > > return try_to_free_buffers(page); > > > } > > > > > > +static int blkdev_writepages(struct address_space *mapping, > > > + struct writeback_control *wbc) > > > +{ > > > + if (dax_mapping(mapping)) { > > > + struct block_device *bdev = I_BDEV(mapping->host); > > > + int error; > > > + > > > + error = dax_writeback_mapping_range(mapping, bdev, wbc); > > > + if (error) > > > + return error; > > > + } > > > + return generic_writepages(mapping, wbc); > > > +} > > > > Can you remind of the reason for calling generic_writepages() on DAX > > enabled address spaces? > > Sure. The initial version of this patch didn't do this, and during testing I > hit a bunch of xfstests failures. In ext2 at least I believe these were > happening because we were skipping the call into generic_writepages() for DAX > inodes. Without a lot of data to back this up, my guess is that this is due > to metadata inodes or something being marked as DAX (so dax_mapping(mapping) > returns true), but having dirty page cache pages that need to be written back > as part of the writeback. > > Changing this so we always call generic_writepages() even in the DAX case > solved the xfstest failures. > > If this sounds incorrect, please let me know and I'll go and gather more data. So I think a more correct fix it to not set S_DAX for inodes that will have any pagecache pages - e.g. don't set S_DAX for block device inodes when filesystem is mounted on it (probably the easiest is to just refuse to mount filesystem on block device which has S_DAX set). Honza -- Jan Kara SUSE Labs, CR