From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:44489 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751940AbdATMn4 (ORCPT ); Fri, 20 Jan 2017 07:43:56 -0500 Date: Fri, 20 Jan 2017 13:23:02 +0100 From: Jan Kara To: Steve Kenton Cc: linux-fsdevel@vger.kernel.org, jack@suse.cz, pali.rohar@gmail.com Subject: Re: Sync took ~8 hours to complete on a UDF DVD+RW with very complex directory structure Message-ID: <20170120122302.GA18224@quack2.suse.cz> References: <20170112003502.11233-1-skenton@ou.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170112003502.11233-1-skenton@ou.edu> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed 11-01-17 18:35:02, Steve Kenton wrote: > I first noticed this with 4.10rc2+ while testing some changes I was > making to the UDF driver but it's neither a new problem nor related to my > changes. Below is a test run on a stock Ubuntu 14.04 system with kernel > 3.19 and the results are the same. If I copy large video files to the DVD > I can put 4+GiB on the disk, it syncs as expected and life is good. If I > try to copy Linus' 2.7GiB repo to the DVD it is still going after running > overnight and after killing the copy sync does not return for hours, > which hangs a graceful reboot. I should note that while the sync has not > completed the filesystem on the DVD seems usable for the light testing I > did using df, ls, find etc and the verbose copy was still proceeding if > slowly when I killed it. Yeah, I think the problem is that seeking just kills the DVD drive and UDF driver in Linux is not very good in avoiding them. So writing to a UDF filesystem on DVD media directly simply does not work very well. Also if you copy a directory tree, there are lots of inplace updates of directories happening so that may contribute to slowness as well. So all in all I don't think this was ever something we were trying to make work reasonably since people don't tend to use DVD like this... Honza -- Jan Kara SUSE Labs, CR