From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f178.google.com (mail-pf0-f178.google.com [209.85.192.178]) by kanga.kvack.org (Postfix) with ESMTP id A5D416B0009 for ; Fri, 12 Feb 2016 23:59:25 -0500 (EST) Received: by mail-pf0-f178.google.com with SMTP id q63so57814708pfb.0 for ; Fri, 12 Feb 2016 20:59:25 -0800 (PST) Received: from mga11.intel.com (mga11.intel.com. [192.55.52.93]) by mx.google.com with ESMTP id bp6si24778418pac.135.2016.02.12.20.59.24 for ; Fri, 12 Feb 2016 20:59:24 -0800 (PST) Date: Fri, 12 Feb 2016 21:59:12 -0700 From: Ross Zwisler Subject: Re: [PATCH v2 0/2] DAX bdev fixes - move flushing calls to FS Message-ID: <20160213045912.GA22595@linux.intel.com> References: <1455137336-28720-1-git-send-email-ross.zwisler@linux.intel.com> <20160211124304.GI21760@quack.suse.cz> <20160212190320.GA24857@linux.intel.com> <20160213023849.GD14668@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160213023849.GD14668@dastard> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Chinner Cc: Ross Zwisler , Jan Kara , 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@lists.01.org, xfs@oss.sgi.com On Sat, Feb 13, 2016 at 01:38:49PM +1100, Dave Chinner wrote: > On Fri, Feb 12, 2016 at 12:03:20PM -0700, Ross Zwisler wrote: > > On Thu, Feb 11, 2016 at 01:43:04PM +0100, Jan Kara wrote: > > > On Wed 10-02-16 13:48:54, Ross Zwisler wrote: > > > > 3) In filemap_write_and_wait() and filemap_write_and_wait_range(), continue > > > > the writeback in the case that DAX is enabled but we only have a nonzero > > > > mapping->nrpages. As with 1) and 2), I believe this is necessary to > > > > properly writeback metadata changes. If this sounds wrong, please let me > > > > know and I'll get more info. > > > > > > And I'm surprised here as well. If there are dax_mapping() inodes that have > > > pagecache pages, then we have issues with radix tree handling as well. So > > > how come dax_mapping() inodes have pages attached? If it is about block > > > device inodes, then I find it buggy, that S_DAX gets set for such inodes > > > when filesystem is mounted on them because in such cases we are IMO asking > > > for data corruption sooner rather than later... > > > > I think I've figured this one out, at least partially. > > > > For ext2 the issues I was seeing were due to the fact that directory inodes > > have S_DAX set, but have dirty page cache pages. In testing with > > generic/002, I see two ext2 inodes with S_DAX trying to do a writeback while > > they have dirty page cache pages. The first has i_ino=2, which is the > > EXT2_ROOT_INO. > .... > > As far as I can see, XFS does not have these issues - returning immediately > > having done just the DAX writeback in xfs_vm_writepages() lets all my xfstests > > pass. > > XFS will not have issues because it does not dirty directory inodes > at the VFS level, nor does it use the page cache for directory data. > However, looking at the code I think it does still set S_DAX on > directory inodes, which it shouldn't be doing. > > I've got a couple of fixes I need to do in this area - hopefully > I'll get it done on Monday. Cool. I've got a quick patch that stops S_DAX from being set on everything but regular inodes for ext2 and ext4. This solved a lot of my xfstests failures. Even after that I'm seeing two last failures with ext4 - I'll keep working on those. - Ross -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org