From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:48353 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932336AbcEQMK4 (ORCPT ); Tue, 17 May 2016 08:10:56 -0400 Date: Tue, 17 May 2016 08:10:23 -0400 From: Vivek Goyal To: Miklos Szeredi , Daniel Axtens Cc: Al Viro , linux-fsdevel , linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org, mpe@ellerman.id.au, dchinner@redhat.com Subject: Re: 45aebeaf4f67 "ovl: Ensure upper filesystem supports d_type" breaking Docker Message-ID: <20160517121023.GA6553@redhat.com> References: <87d1ombix6.fsf@gamma.ozlabs.ibm.com> <20160516130727.GA26411@redhat.com> <20160517062829.GG14480@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, May 17, 2016 at 10:15:21AM +0200, Miklos Szeredi wrote: > On Tue, May 17, 2016 at 8:28 AM, Al Viro wrote: > > On Mon, May 16, 2016 at 09:07:27AM -0400, Vivek Goyal wrote: > >> So it became clear that we need a check at mount time to make sure > >> d_type is supported otherwise error out. This will require users to > >> do mkfs.xfs with ftype=1 to make progress. > >> > >> I think new defaults for mkfs.xfs are such that ftype=1 is set. I am > >> not sure which version that change was made in. > > > > Dumb question - can we end up with empty workdir at that point? Because > > if we do, the check would appear to return a false negative, no matter > > what fs supports... > > ovl_workdir_create() creates a subdirectory of workdir ("work") so > workdir itself won't be empty after that. If somebody else messes > with workdir, then we are screwed anyway. Right. Initially I was creating a directory of my own and later realized that ovl_workdir_create() already creates one. Having said that, what happens when ovl_workdir_create() fails and we mount overlayfs read only. In that case I think we will conclude that underlying fs does not support d_type and mounting will fail. Any thoughts, on how to handle this failure path better? Daniel, Yesterday Eric Sandeen told me that I can run "xfs_info " to figure out if ftype is 0 or 1. You might want to run "xfs_info /" and ensure ftype=0 in your case and overlay is not detecting it wrong. Thanks Vivek