From: tytso@mit.edu Subject: Re: 2.6.33.1: ext4 disk free weirdness Date: Mon, 29 Mar 2010 10:53:11 -0400 Message-ID: <20100329145311.GA4671@thunk.org> References: <20100329045748.GR2657@zip.com.au> <4BB0BDD2.3080100@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: CaT , linux-ext4@vger.kernel.org To: Eric Sandeen Return-path: Received: from thunk.org ([69.25.196.29]:36497 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754105Ab0C2P4h (ORCPT ); Mon, 29 Mar 2010 11:56:37 -0400 Content-Disposition: inline In-Reply-To: <4BB0BDD2.3080100@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Mar 29, 2010 at 09:48:50AM -0500, Eric Sandeen wrote: > CaT wrote: > > Using kernel 2.6.33.1. Am rsyncing from /data/mirror (a raid0 mount) to > > /dev/sda1 (a usb HD). Both filesystems formatted as ext3 but mounted as > > ext4. /mnt filesystem is only being added to and currently large files > > (iso files 700MB-4.4GB) are being copied. When I remounted /mnt as ext3 > > I could not duplicate the issue and the amount of disk used stabilised > > at 182G. The df results, whilst /mnt is mounted as ext4, are below: > > I would say this is likely speculative allocation due to delalloc > (ext4 has to reserve worst-case metadata amounts to prepare for > delalloc writeback). When the file data actually gets written out, > the worst-case reservation is freed up again. We also flush and > switch to nodelalloc when the filesystem is pretty close to full. > see ext4_nonda_switch() for example. > > This looks pretty severe though, more than I would expect > from that behavior. This is fixed in commit d330a5bef, which which got merged post 2.6.34-rc2, and which we need to get into 2.6.33 stable. If you cherry-pick that commit, I think you'll see that it fixes this problem. - Ted